What Color Is Your Cuneus?

Career counseling via voxel-based morphometry? With the U.S. unemployment rate at 9.5% as of June 2010, job seekers might be willing to try anything to gain an edge. As part of the Trends in Phrenology craze sweeping the field, the Johnson O’Connor Research Foundation appears to be capitalizing on the new cultural neurophilia:

The Johnson O'Connor Research Foundation is a nonprofit scientific research and educational organization with two primary commitments: to study human abilities and to provide people with a knowledge of their aptitudes that will help them in making decisions about school and work. Since 1922, hundreds of thousands of people have used our aptitude testing service to learn more about themselves and to derive more satisfaction from their lives.

Sounds noble, right? Although they are a nonprofit, JOCRF charges $675 ($750 in New York)¹ for a proprietary assessment battery. And a very preliminary morphometric analysis by Haier et al. (2010) features prominently on their homepage. The genesis of this structural MRI study is helpfully described on their website.

Relationships Between Aptitudes and Brain Areas

...In late 2006 at a professional research conference, David Ransom, exploring how our founder’s vision could be pursued by funding an outside researcher through the Johnson O’Connor Research Support Corporation, discussed with Dr. Richard Haier, a leading researcher on brain imaging and intelligence, the possibility of relating the volumes of defined brain areas measured with structural magnetic resonance imaging (sMRI) to performance on Johnson O’Connor aptitude tests. In the spring of 2007 Dr. Haier agreed to work on such a study, and in conjunction with Mt. Sinai Medical Center in New York, to conduct sMRI scans of 40 Foundation examinees, under the supervision of Dr. Cheuk Tang.

In the summer of 2007 a sample of Foundation clients aged 18 to 35 was recruited to participate in the study by having scans completed at Mt. Sinai. These examinees were selected in two ways. First, a solicitation letter was sent to former clients tested in New York in the previous year and a half. Second, new examinees were recruited in person when they came in for testing.

In January 2008 the goal of 40 examinees with completed sMRI scans and Johnson O’Connor test scores was met. Dr. Tang sent the brain-scan data for the examinees to Dr. Haier, and Chris Condon sent along the corresponding aptitude test data. Working with the sMRI scans, Dr. Haier used recently-developed technology called “voxel-based morphometry” to identify various brain areas and measure the volume of gray and white matter in each area.

In addition to the structural MRI, each participant received the following cognitive tests:

The eight tests in the JOCRF battery were: Inductive Speed (IS), Analytical Reasoning (AR), Number Series (NS), Number Facility (NF), Wiggly Block (WB), Paper Folding (PF), Verbal-associative Memory (VM), and Number Memory (NM). Each is described in Additional file 1: supplemental table S1 [.DOC]. These tests have been used in research on various aspects of cognition and intelligence [e.g., Schroeder & Salthouse, 2004].

A confirmatory factor analysis was performed using the entire psychometric database from 2002-2003, consisting of 6,889 people who had visited JOCRF for vocational guidance and aptitude tests. Combining this group with the 40 MRI subjects, the analysis revealed loadings for g (general intelligence) and four other factors: Speed of Reasoning (IS, AR), Numerical (NS, NF), Spatial (WB, PF), and Memory (VM, NM). Using standard voxel-based morphometry methods (Ashburner & Friston, 2000), the authors correlated gray matter volumes with each of these independent factors.

However, with n=40 the study was underpowered to produce much in the way of significant results, which accounts for why it was published in BMC Research Notes. I have no problem with that, once we're clear on the scope of the journal:

The aim of BMC Research Notes is to reduce the loss suffered by the research community when results remain unpublished because they do not form a sufficiently complete story to justify the publication of a full research article. A key objective of the journal is to ensure that associated data sets are published in standard, reusable formats whenever possible. Data sets published in the journal will be made searchable and easy to harvest for reuse.

Press releases and news stores were not very clear on this point, however:

Brain Scans Could Guide Career Choices

By Jeanna Bryner, LiveScience Managing Editor

Brain scans may guide a person toward the optimal career, new research suggests.

The results show people's cognitive strengths and weaknesses are linked to differences in the volume of gray matter in certain parts of the brain.

And this!

MRI challenges Myers-Briggs

By Rebekah Moan

Good news radiologists! There’s a new place to set up that MRI machine: the guidance counselor’s office. Researchers are starting to use MRI to document an individual’s ability to perform on vocational guidance tests.

I see.

There should be some sort of prominent disclaimer when the popular press reports on such preliminary findings, but we find nothing of the sort. Instead we'll have pushy overbearing parents clamoring for that MRI to give their kid the advantage needed to get into Harvard.

Let's return to the actual methods and results reported in the article (which is open access for all you science writers out there):

Given the limited statistical power of 40 subjects, we detail results at p<.001, uncorrected, in all the tables...; figures are shown consistently for all analyses at p<.01 uncorrected, to allow straightforward comparisons. Findings corrected using the False Discovery Rate (FDR) p<.05 are noted; no findings survived correction using Family Wise Error (FWE).

Table 1 gives the full list of brain areas that showed non-significant positive correlations between gray matter volume and the factors of g, Speed of Reasoning, Numerical, and Spatial. The Memory factor did show significant negative correlations with some regions, as shown below [note that a higher memory score was associated with smaller gray matter volumes]:


Table 1 (modified from Haier et al., 2010). Brain areas with significant negative gray matter correlations (p<.001 uncorrected) with the Memory factor. * BA is Brodmann Area, Talairach x, y, z co-ordinates; positive x values are in right hemisphere; Z is z-score; cluster size is number of voxels (blank entry denotes part of previous cluster); FDR is False Discovery Rate (blank entry denotes not significant p<.05).

How did the authors interpret these negative correlation?

The inverse direction of the gray matter correlations for the Memory factor was evident in both component tests, although we are unaware of any previous reports of inverse correlations between gray matter and other similar tests. ... Since there are previous reports of sex differences in the patterns of gray matter correlates to intelligence test scores, we recomputed these analyses for males and females separately. Only the males showed the inverse pattern. Why this should be the case is not clear. ... Since the sample sizes, however, were quite small for VBM stability (21 males, 19 females), we cannot interpret this finding with confidence. In general, VBM requires larger samples than 40 for stability, so this report is offered as an exploratory account of factor versus test correlates with gray matter in a sample uniquely characterized with a comprehensive test battery.

In brief: the authors are unable to interpret this finding! So don't rush out just yet for that MRI offered by the local entrepreneurial neuroradiologist who set up shop in the guidance counselor’s office.


Footnote

¹ Their website says this is their first fee increase since Jan 1, 2003. "For years now, we have been offering—and will continue to offer—the testing below our cost."

References

Ashburner J, Friston KJ. (2000). Voxel-based morphometry--the methods. Neuroimage 11:805-21.

Haier, R., Schroeder, D., Tang, C., Head, K., & Colom, R. (2010). Gray matter correlates of cognitive ability tests used for vocational guidance. BMC Research Notes, 3 (1) DOI: 10.1186/1756-0500-3-206

Schroeder DH, Salthouse TA. (2004). Age-related effects on cognition between 20 and 50 years of age. Personality and Individual Differences 36:393-404.

Odor Judge. From Ten Odd Jobs. Which One Do YOU Want?

Remembering Dr. Robert Galambos

Robert Galambos, Neuroscientist Who Showed How Bats Navigate, Dies at 96

By DOUGLAS MARTIN
Published: July 15, 2010

Dr. Robert Galambos, a neuroscientist whose work included helping to prove how bats navigate in total darkness and deciphering the codes by which nerves transmit sounds to the brain, died June 18 at his home in the La Jolla section of San Diego. He was 96.

UCSD's Nick Spitzer hosts neuroscientist Bob Galambos a pioneer in understanding fundamental principles of the auditory system. Series: "UCSD Guestbook" [11/2002] [Science] [Show ID: 6646]

As a graduate student at Harvard in 1939, Robert Galambos made a name for himself with a pioneering experiment involving flying bats and their use of sound waves to navigate in the dark.

In the decades that followed, Dr. Galambos was head of neurophysiology research at the Walter Reed Army Research Institute and was a founding member of the neurosciences department at the University of California, San Diego, where he mentored many scientists. In the 1980s, he developed a hearing test for infants and in recent years he conducted research on how the eye and brain work together to produce visual images.

-from the Obituary by Blanca Gonzalez, UNION-TRIBUNE STAFF WRITER

Film on bat echolocation made in 1940 by Bob Galambos and Don Griffin. Narration by Dr. Galambos.

Tales of Passion and Disgust

Robert Mapplethorpe - St. Sebastian

The previous post (Pleasure or Pain?) described the visual stimuli and behavioral results (subjective emotional ratings) from an experiment examining brain activity in response to pictures from four categories: neutral, disgust-inducing, erotic, and sadomasochistic (Stark et al., 2005). The participants were 24 adults, 12 of whom identified as having sadomasochistic sexual preferences (SM) and 12 without (non-SM).

Some of the results were of no surprise to anyone. The emotion ratings for neutral and disgust-inducing stimuli did not differ between the two groups. As expected, however, ratings for the other two stimulus classes were divergent:

The erotic pictures revealed more positive affect, more arousal, and more sexual arousal for the nonSM group in comparison to the SM group. SM subjects indicated to have felt more positive, more dominant, less disgusted, and more sexually aroused during the presentation of the pictures with sadomasochistic content than the nonSM subjects.

Why conduct this study in the first place, you ask? One reason given by the authors is to examine the neural correlates of two motivational systems, the approach and withdrawal systems (Cacioppo & Gardner, 1999). The withdrawal (or avoidance) system is triggered by threats in the environment, including those inducing fear and disgust, while the approach (or appetitive) system promotes feeding, sexual activity, and social behavior. Everyone in Stark et al.'s experiment wanted to avoid rotting hamburgers, but only the non-SM participants wanted to avoid sadomasochistic images. Thus, the same exact stimulus class induced different approach and avoidance responses in two groups of people with divergent sexual preferences.

I would add that a broader societal function of such a study might be to educate and to reduce stigma. A greater understanding of people different from ourselves makes for a more accepting and tolerant populace.

What about the possibility of viewing similar images in different contexts? A painting of St. Sebastian in a cathedral vs. Mapplethorpe's Sebastian in a retrospective at the Whitney? A flogging scene from The Passion of the Christ vs. a flogging scene in a dungeon? Interestingly, some of the most fervent supporters of the former are the most rabid critics of the latter (Frank Rich provides examples in The Good News About Mel Gibson).

Disgust and Morality

This brings us back to the possible evolutionary basis of disgust. Since this emotion is a response to things that are physically distasteful or morally repugnant, disgust has been examined in a specific evolutionary framework: "from oral to moral" (Rozin et al., 2009) -- from the rejection of bitter tastes to being grossed out by bugs to being repelled by certain social groups or sexual acts (Haidt & Hersh, 2001). Are there identical brain systems underlying these emotional responses? To answer this question, the most important comparison is the one between sadomasochistic and disgust-inducing images in the non-SM group.

Several T-contrasts were calculated for each subject: the emotional conditions versus the neutral condition (Disgust <> Neutral, Erotic <> Neutral, Sm <> Neutral), and for the positive emotion versus negative emotion (Erotic <> Disgust, Sm <> Disgust, Sm <> Erotic).

For each of the six contrasts above, there were two within-group comparisons and one between-group comparison for 20 regions of interest (ROIs), which were selected from a meta-analysis on neuroimaging studies of emotion (Phan et al., 2002). Exploratory analyses were performed as well. That's an awful lot of comparisons! [requiring stringent correction, of course]. The power to detect differences was reduced further by small group sizes (n=12 for each), rather diverse subject groups, and the use of stimuli that weren't terribly potent at eliciting some of the desired effects. Compare the relatively tame images used here (no explicit presentation of the genitals) to the 3 minute porn films of Zhang et al. (see Erotic or Disgusting?).

With all these caveats in mind, what were the results? For the Disgust vs. Neutral comparison, there were no significant differences between the groups, which matches their behavioral ratings. For Erotic vs. Neutral, there was greater activation for non-SM participants in the ventral striatum (known as a reward-related area), the hypothalamus, (controls many metabolic and endocrine functions) and the thalamus (a sensory and motor "relay station"). Ratings for the erotic pictures were similar in the two groups for dominance and disgust but higher in valence, arousal, and sexual arousal for the non-SM group. For Sm vs. Neutral, the SM group showed extensive activations in a number of frontal, temporal, and subcortical regions, including (most bizarrely) the insula, which has been associated with disgust. The only significant between-group difference, however, was in the ventral striatum. And the non-SM group didn't seem to activate any "disgust-related" regions, perhaps because many of them weren't actually disgusted by those images -- rated only 4.25 on a 9-point scale (1=very low and 9=very high). The variability was large, though, which prevented a statistically significant difference between Sm and disgust-inducing pictures (the latter rated 6.67 on disgust).

I think this level of variability in disgust reactions to the Sm images compromises the all-important Sm <> Disgust contrast in the non-SM group. But for what it's worth, right anterior cingulate showed greater activation to disgust pictures, whereas left posterior cingulate showed greater activation to sadomasochistic pictures. In the SM participants, the same contrast revealed greater activity in frontal, temporal/occipital, and subcortical structures (ventral striatum, thalamus, and brainstem). The between-group comparison again demonstrated the obvious: Sm pictures were more rewarding for the SM participants than for their non-SM counterparts.

I'm not sure how to interpret the cingulate findings, so I'll let the authors speak for themselves... Oh, wait, they didn't say anything about that, either. Ultimately, this study needed more potent stimuli (films instead of stills) and larger subject groups to avoid any sex-related differences in disgust sensitivity.

References

Cacioppo JT, Gardner WL. (1999). Emotion. Annu Rev Psychol. 50:191-214.

Haidt J, Hersh MA (2001). Sexual morality: The cultures and emotions of conservatives and liberals. J Applied Social Psychol. 31:191–221.

Phan KL, Wager T, Taylor SF, Liberzon I. (2002). Functional neuroanatomy of emotion: a meta-analysis of emotion activation studies in PET and fMRI. Neuroimage 16:331-48.

Rozin P, Haidt J, Fincher K. (2009). Psychology. From oral to moral. Science 323:1179-80.

STARK, R., SCHIENLE, A., GIROD, C., WALTER, B., KIRSCH, P., BLECKER, C., OTT, U., SCHAFER, A., SAMMER, G., & ZIMMERMANN, M. (2005). Erotic and disgust-inducing pictures—Differences in the hemodynamic responses of the brain. Biological Psychology, 70 (1), 19-29 DOI: 10.1016/j.biopsycho.2004.11.014

Zhang, M., Hu, S., Xu, L., Wang, Q., Xu, X., Wei, E., Yan, L., Hu, J., Wei, N., & Zhou, W. (2010). Neural circuits of disgust induced by sexual stimuli in homosexual and heterosexual men: An fMRI study. Eur J Radiol. Jun 22. [Epub ahead of print].

With its laborious build-up to its orgasmic spurtings of blood and other bodily fluids, Mr. Gibson's film is constructed like nothing so much as a porn movie, replete with slo-mo climaxes and pounding music for the money shots. Of all the "Passion" critics, no one has nailed its artistic vision more precisely than Christopher Hitchens, who on "Hardball" called it a homoerotic "exercise in lurid sadomasochism" for those who "like seeing handsome young men stripped and flayed alive over a long period of time."

-Frank Rich, Mel Gibson Forgives Us For His Sins [March 7, 2004]

Pleasure or Pain?

Robert Mapplethorpe - Untitled (Self Portrait)

The previous post (Erotic or Disgusting?) covered a functional MRI experiment on the neural responses to erotic films in heterosexual and homosexual males (Zhang et al., 2010). Specifically, the study examined sexual arousal and disgust while the participants viewed various types of porn. Neuroimaging results were reported only for the stimuli deemed distasteful by each group, wherein the left ventromedial prefrontal cortex was more active for gay men, and the left cuneus [visual cortex] was more active for straight men. It was unclear why this particular outcome was obtained. Other problems with the paper included the comparison condition (passive rest, rather than viewing neutral film clips) and the analysis strategy.

An earlier study, however, took a more comprehensive look at arousal and disgust in a different sexual minority group: those with sadomasochistic preferences, who were compared to those without (Stark et al., 2005). Here, the stimuli were pictures from four categories: neutral, disgust-inducing, erotic, and sadomasochistic:

The erotic pictures included either pictures of single naked subjects or pictures of couples in an intimate situation. The pictures with sadomasochistic content either had a submission/dominance theme (e.g. a naked man pulling a coach with a dressed woman), or showed sadomasochistic techniques (e.g. hurting someone with hot wax, pictures of bound subjects). The scenes depicted single subjects (male and female), couples, and groups of subjects.

The disgust-inducing pictures showed a broad range of different disgust elicitors: unusual food (e.g. man eating a grasshopper, man biting into a monkey head), disgusting animals (e.g. snails, maggots), poor hygiene (e.g. dirty toilet, garbage piles, and body products (e.g. excrements, vomit). Neutral pictures showed household articles, geometric figures, and nature scenes.

This allowed within-subject and between-subject approaches in the same experiment. Presumably, rotting garbage would be disgusting to everyone, while the groups would differ in their reactions to images with erotic or sadomasochistic content.

Participants were 24 adults, 12 of whom identified as having sadomasochistic sexual preferences (SM)¹ and 12 without sadomasochistic preferences (non-SM). Each group was comprised of 6 men and 6 women. Subjects were initially classified by asking, “Are you interested in sadomasochistic sexual activities?” This was followed by an 8 item questionnaire asking about sexual orientation, identity, and experiences, with each item rated on a 5-point scale (e.g., “I describe myself as a sadomasochist”, “I describe myself as sadistic/dominant”, etc.).

All pictures were rated in advance by separate groups of SM and non-SM participants on the dimensions of disgust and sexual arousal using 9-point visual analog scales, and on valence, arousal, and dominance using the self-assessment manikin (also on a scale from 1 to 9). The scanned subjects also rated the pictures after the fMRI experiment was over. The emotional ratings for neutral and disgust-inducing stimuli did not differ between the two groups. As expected, however, ratings for the other two stimulus classes were divergent:

The erotic pictures revealed more positive affect, more arousal, and more sexual arousal for the nonSM group in comparison to the SM group. SM subjects indicated to have felt more positive, more dominant, less disgusted, and more sexually aroused during the presentation of the pictures with sadomasochistic content than the nonSM subjects.

Statistically speaking, emotion ratings for the disgust-inducing and sadomasochistic images did not differ in the non-SM group.² On the other hand, ratings for the sadomasochistic pictures in the SM participants were similar to those for erotic pictures in the non-SM group. These findings were important for the between-subjects comparison of disgust and sexual arousal.

During the fMRI experiment, each category of pictures was presented in separate blocks. Subjects were instructed to “let the pictures affect you”. For data analysis purposes, a number of different comparisons were performed:

Several T-contrasts were calculated for each subject: the emotional conditions versus the neutral condition (Disgust <> Neutral, Erotic <> Neutral, Sm <> Neutral), and for the positive emotion versus negative emotion (Erotic <> Disgust, Sm <> Disgust, Sm <> Erotic). For a random effect analysis the individual contrast images (first level) were used in a second level analysis.

As you can imagine, the amount of data reported in this paper is voluminous. Brain regions of interest (ROIs) were selected from the meta-analysis of Phan et al. (2002) on neuroimaging studies of emotion. Exploratory analyses were performed as well.

The Erotic or Disgusting? Pleasure or Pain? series will conclude next time with the functional neuroanatomy associated with states of disgust and sexual arousal in those with vanilla and BDSM preferences.

Footnotes

¹ Specific orientations were as follows:

In the SM group three subjects reported a bisexual orientation (two male, one female). Furthermore, the SM group could be separated into eight masochists (four female), one sadist (female) and three switchers (one female).

² Numerically speaking, however, disgust ratings were higher for the former than for the latter (6.67 vs. 4.25).

References

Phan KL, Wager T, Taylor SF, Liberzon I. (2002). Functional neuroanatomy of emotion: a meta-analysis of emotion activation studies in PET and fMRI. Neuroimage 16:331-48.

STARK, R., SCHIENLE, A., GIROD, C., WALTER, B., KIRSCH, P., BLECKER, C., OTT, U., SCHAFER, A., SAMMER, G., & ZIMMERMANN, M. (2005). Erotic and disgust-inducing pictures—Differences in the hemodynamic responses of the brain. Biological Psychology, 70 (1), 19-29 DOI: 10.1016/j.biopsycho.2004.11.014

Erotic or Disgusting?

What's hot? What's not? What do you consider unappealing?

A greater understanding of people different from ourselves makes for a more accepting and tolerant populace. Are attempts to deliberately evoke disgust by the sexual practices of "others" an important and worthy step towards achieving this goal? Or does it further stigmatize the minority "outgroup"? What if the "outgroup" is disgusted by the practices of the majority?

Different strokes for different folks
And so on and so on and scooby dooby dooby

Everyday People
------Sly & The Family Stone

Brain Responses to Erotic Films

What are the neural correlates of sexual arousal and disgust in heterosexual men and homosexual men viewing various types of porn (Zhang et al., 2010)? "Where can I sign up?" you say, both as a participant and a researcher. Or maybe you're horrified that such an experiment would be conducted by the scientific establishment. Pornography is a hot-button topic, and a discussion of its potential harms and merits is well beyond the scope of this post.¹

Disgust is considered to be one of the six basic emotions (Ekman, 1992). Given that disgust is a response to things that are physically distasteful or morally repugnant, this emotion has been examined in a specific evolutionary framework: "from oral to moral" (Rozin et al., 2009):

According to the principle of preadaptation, a system that evolves for one purpose is later used for another purpose. From this viewpoint, disgust originates in the mammalian bitter taste rejection system, which directly activates a disgust output system. This primal route (e.g., bitter and some other tastes) evokes only the output program, without a disgust evaluation phase. During human evolution, the disgust output system was harnessed to a disgust evaluation system that responded not to simple sensory inputs (such as bitter tastes) but to more cognitively elaborated appraisals (e.g., a cockroach). ... Later, through some combination of biological and cultural evolution, the eliciting category was enlarged to include reminders of our animal nature, as wel [sic] as some people or social groups.

In a rationale that is simple yet puzzling, Zhang et al. wished to see if the brains of gay men process disgust in a different manner from those of straight men.²

To our knowledge, there have been few studies concerning the [sic] disgust in homosexual men. Whether the patterns of disgust differ between homosexual and heterosexual men is unknown.

The participants were 16 heterosexual and 16 homosexual men (as identified by self-report). Bisexuals were excluded. The stimuli were 3 minute long film clips depicting explicit sexual activity between two men (M-M), two women (F-F), or a woman and a man (F-M). "Each type of erotic film was montaged with attractive short films." Subjects passively watched the films during scanning, then rated their levels of sexual arousal and sexual disgust after the fMRI portion had finished (shown below).


Fig 1 (Zhang et al., 2010). Mean scores of the sexual films showing F–F, F–M and M–M in the two groups. F–F and M–M stimuli induce sexual disgust, respectively. Results of two independent samples test comparisons (homosexual versus heterosexual) are displayed. Blue indicates homosexual men; green, heterosexual men; the asterisk, p less than 0.01. Error bars equal 1 SD. NOTE: the level of sexual disgust was assessed by scores from 1 (extremely high) to 4 (extremely low), and the level of sexual arousal was rated from 6 (extremely low) to 9 (extremely high).

It was no surprise to anyone that straight men were most turned on by F-M film clips and turned off by the M-M films. Straight guys were also a bit turned on by F-F (also not surprising given the popularity of girl-on-girl p0rn), although there was a great deal of variability. Also as expected, gay men were most aroused by M-M films. They rated their disgust as highest for F-F clips but were close to neutral for heterosexual p0rn (interestingly).³

The neuroimaging data were analyzed using Disgust versus Rest as the comparison of interest.

In the homosexual group, the F–F stimulus identified great activity in a large number of brain regions, including the left superior frontal gyrus, right and left medial frontal gyrus, left and right cerebellum, left middle occipital gyrus (BA 19), right lingual gyrus (BA 18), left precuneus, right middle temporal gyrus, left superior temporal gyrus (BA 38), left thalamus, and left supplementary motor area.

In the heterosexual group, M–M stimuli elicited great activations in the left middle frontal gyrus, right middle frontal gyrus (BA 6), left inferior frontal gyrus (BA 45), right inferior frontal gyrus (BA 47), left middle temporal gyrus, right middle temporal gyrus (BA 37, BA 39), left superior temporal gyrus (BA 13), right superior temporal gyrus (BA 38), left inferior occipital gyrus (BA 18), bilateral caudate, bilateral thalamus, bilateral insula, left putamen, right parahippocampal gyrus, right cerebellum, right anterior cingulate (BA 42), and right amygdala.

OK, so that's a bunch of areas that are activated relative to doing nothing (instead of relative to watching a neutral film). I won't try to interpret those results. How about comparing the Disgust vs. Rest responses of the gay and straight men? There was one region of the brain more active in each of the groups: left ventromedial prefrontal cortex for gay men (Fig. 4), and left cuneus [visual cortex] for straight men (Fig. 5).


Fig. 4 (modified from Zhang et al., 2010). Aversive sexual stimuli compared to rest: stronger brain activation in homosexual men compared to heterosexual men in the left medial frontal gyrus (maximum at −1, 39, −12).



Fig. 5 (modified from Zhang et al., 2010). Aversive sexual stimuli compared to rest: stronger brain activation in heterosexual men compared to homosexual men in the left cuneus (maximum at −1, −81, 36). [two-sample t-test, p less than 0.001 uncorrected, extend 5 voxels]


Why?? What does it mean?

The MPFC [media prefrontal cortex] engages in a number of processes, which are potentially common to various emotional tasks (e.g. appraisal/evaluation of emotion, emotional regulation, and emotion-driven decision-making). Notably, ROI analysis showed that the negative correlation was found between magnitude of MRI signals in the left media frontal gyrus and the level of disgust in homosexual men...

Why were the gay men better able to downregulate their emotional responses to unpleasant p0rn [if you believe that negative correlation]? Why would the heterosexual males engage imagery processes to a greater extent than homosexual males when viewing sexual acts they find distasteful? (as suggested by the authors suggest below).

...Activity in this occipital region [cuneus] might reflect more vivid mental imagery induced by viewing disgusting stimuli, specifically when videos were watched... Thus, in the present study, the activation of the left cuneus in heterosexual men may reflect a combination of external viewing and internal generation of disgusting images.

In the absence of a full report on the data that includes additional comparisons (disgusting versus neutral and arousing films), I'll refrain from commenting further. Perhaps other published studies will be able to shed light on the matter, as we'll see in the next post.


Footnotes

¹ For further reading (and a range of viewpoints), see the following:

THIRD of children have seen online porn by the time they are 10, shocking study reveals

Think critically when looking at statistics (A valuable lesson, now with porn!)

Porn: Good for us?

Scientific examination of the subject has found that as the use of porn increases, the rate of sex crimes goes down.

The truth about the porn industry

Gail Dines, the author of an explosive new book about the sex industry, on why pornography has never been a greater threat to our relationships

Finally, anything by Dr Petra on the topic would be recommended...

² Although not explicitly stated, it seems that they wanted to determine whether gay men respond more like straight men or straight women, since the latter have stronger reactions to disgust.

³ Therefore, the gay men in this study were not disgusted by the practices of the majority.


References

Ekman P. (1992). Are there basic emotions? Psychol Rev. 99:550-3.

Rozin P, Haidt J, Fincher K. (2009). Psychology. From oral to moral. Science 323:1179-80.

Zhang, M., Hu, S., Xu, L., Wang, Q., Xu, X., Wei, E., Yan, L., Hu, J., Wei, N., & Zhou, W. (2010). Neural circuits of disgust induced by sexual stimuli in homosexual and heterosexual men: An fMRI study. European Journal of Radiology DOI: 10.1016/j.ejrad.2010.05.021

Mary Millington & co-star Alan Lake share a private moment
in 1978's The Playbirds

Living and Forgetting

And I'll be easy
Like living and forgetting
And if I pick you up
I'll be sure to let you down

-Living and Forgetting, Glasstown (mp3)

Forgetting Emotional Information Is Hard

Our memory for emotional events is generally better than our memory for neutral events. This is a key issue in developing treatments for post-traumatic stress disorder. How do we rid ourselves of unpleasant memories? In structured laboratory environments, the best way to forget is intentional inhibition during the encoding phase, when exposed to the material for the first time. In other words, engage in a deliberate strategy to forget while the event is actually occurring, as shown in a recent study by Nowicka and colleagues. This process is effortful, and it engages a larger proportion of the brain when the material is emotionally laden (i.e., negative pictures from the International Affective Picture System, or IAPS), relative to when it is neutral (Nowicka et al., 2010).

In the study phase, intention to forget and successful forgetting of emotionally negative images were associated with widespread activations extending from the anterior to posterior regions mainly in the right hemisphere, whereas in the case of neutral images, they were associated with just one cluster of activation in the right lingual gyrus [occipital cortex]. Therefore, forgetting of emotional information seems to be a demanding process that strongly activates a distributed neural network in the right hemisphere. In the test phase, in turn, successfully forgotten images—either neutral or emotionally negative—were associated with virtually no activation... These results suggest that intentional inhibition during encoding may be an efficient strategy to cope with emotionally negative memories.

However, "directed forgetting" is usually not a practical strategy when real life events are unfolding. Whether it can effectively occur at all during horrible tragedies is highly controversial (e.g., Terr vs. Loftus). The phenomenon is more often studied when applied to the retrieval of traumatic or unwanted memories (Anderson & Levy, 2009; Geraerts & McNally, 2008; Levy & Anderson, 2008), not during the encoding phase.


How to Forget

Obviously, it’s unethical to expose people to traumatic events for experimental purposes. Instead, the present study used an item-method directed forgetting task in the lab and measured brain activity with fMRI (Nowicka et al., 2010). Twenty-three participants¹ viewed a set of images from the IAPS that were either negative or neutral in content. During the initial encoding phase, participants were instructed to either REMEMBER or FORGET each picture by means of a cue that was presented after the item appeared on the screen. Then in the memory test phase, these previously presented pictures were intermixed with new ones, and the subjects were told to indicate whether they recognized them or not, regardless of the previous task cue.

Trials were sorted according to task instruction (Remember or Forget) and memory outcome (Remembered or Forgotten). Behavioral data showed that the directed forgetting manipulation was successful. Participants remembered fewer pictures in the To-Be-Forgotten (TBF) condition than in the To-Be-Remembered (TBR) condition. The valence manipulation appeared to be successful as well: recognition was better for emotional pictures, especially in the TBF condition. However, the rate of "false alarms" (incorrect responses to new items) was higher for emotional pictures as well (see figure below). This suggests a bit of a response bias: participants were more likely to say "yes I saw it before" for emotional images than for neutral.


Figure 1B (modified from Nowicka et al., 2010). Percentage of correctly recognized TBR and TBF images (TBR_R and TBF_R, respectively) and percentage of false alarms for the group of 16 subjects included in the fMRI analyses. Bars represent SD; E, emotionally negative images; N, neutral images.

When corrected for false alarm rate, it appears that recognition accuracy was actually lower for the To-Be-Forgotten emotional pictures, meaning they were easier to forget [unless I'm missing something here]. Hmm.

On to the fMRI data. The major analysis was done in relation to the FORGET vs. REMEMBER cue. Was there differential activity when trying to forget an emotional picture compared to a neutral picture? Figure 2A shows the answer: yes, there was greater activity in the bilateral occipital cortex and elsewhere in the right hemisphere for emotional pictures, with only a small occipital focus of activation for the neutral ones.


Figure 2 (modified from Nowicka et al., 2010). The study phase. (A) Effect of memory instruction: intention to forget contrasted with intention to remember (F instruction > R instruction for all trials). Significant group activations are superimposed on a normalized single subject's T1 image.

This indeed suggests that the intention to forget an emotional image (such as a car crash or mutilated body) is more effortful for the brain than trying to forget a neutral landscape scene. During the memory test, however, it didn't matter if you forgot the picture on purpose or by accident -- the neural response to forgotten items was identical to the response produced by entirely new images. Nary a trace [at least as a change in BOLD signal]. Have other investigators found this as well? What does it all mean?

In conclusion, the findings of this item-method directed forgetting fMRI study reveal that forgetting of emotional information is supported by a widely distributed neural network, indicating more effort than forgetting of neutral information. These differences were observed in the study phase but not the test phase, which suggests that the directed forgetting effect is mainly based on inhibition at the encoding level rather than at retrieval (but see: Ullsperger et al. 2000; Nowicka et al., 2009). More generally, our results suggest that flexible control of memory may be effective even in case of unpleasant memories, but still it requires more effort than in case of neutral ones.

"...people's material technologies of memory are always - though much more openly in some cultures than in others - also their technologies of forgetting."

--Review in The Journal of the Royal Anthropological Institute

Footnote

¹ Seven were excluded for insufficient task performance.

References

Anderson MC, Levy BJ. (2009). Suppressing unwanted memories. Curr Dir Psychol Sci. 18:184-194.

Geraerts E, McNally RJ. (2008). Forgetting unwanted memories: directed forgetting and thought suppression methods. Acta Psychol (Amst). 127:614-22.

Joslyn S, Carlin L, Loftus EF. (1997). Remembering and forgetting childhood sexual abuse. Memory 5:703-24.

Levy BJ, Anderson MC. (2008). Individual differences in the suppression of unwanted memories: the executive deficit hypothesis. Acta Psychol (Amst). 127:623-35.

Nowicka, A., Marchewka, A., Jednorog, K., Tacikowski, P., & Brechmann, A. (2010). Forgetting of Emotional Information Is Hard: An fMRI Study of Directed Forgetting Cerebral Cortex DOI: 10.1093/cercor/bhq117

Terr LC (1991). Childhood traumas: An outline and overview. Am J Psychiatry 148:10–20.

Writing Is An Aid To Memory, Lyn Hejinian

I would add greatly to the beauty by those feeling conversant; o where to put them. With its indispensable side, where nothing is greater, the laws of shadowy detail, to the smallest detail, even of the corpses of criminals held long in prison, as inhuman medicine, sketching the action from the insides of the bones and exploring what has been a mind, unknown. I am pressed with questions as if posed and feverish with a peculiar greed. Incessant knowledge and the natural sciences of difficulty, brilliance, complexity, and generosity, to please an entire face, where sorrow by the fact is not of true greatness. Work is retarded by such desire, which is anticipation of its certainty, and hence a desire impossible of satisfaction, in the future despite the grand decision to pull it present. It was that interest as lapse of time, that wanting to put too much in is forgetting, or forgotten calling attention. The whole has been given away and looking out is a forgetting sent without to end all the commoner. The trees of street are laid down. A bedroom is cut where I went. Where I mean to will have to come to me. Though we keep company with cats and dogs, all thoughtful people are impatient, with a restlessness made inevitable by language.