Wednesday, May 26, 2010

Short Cuts

There is way too much to blog about these days. I can't decide among these 3 new papers:

Sometimes, Categorical Statements about Prefrontal Neurons Are Just Wrong

(1) Earl K. Miller (2007) in The Prefrontal Cortex: Categories, Concepts, and Cognitive Control (PDF):
There was virtually no category effect across the ITC [inferior temporal cortex] population and no examples of neurons whose activity showed the sharp across-distinction/within-category generalization that is the behavioral signature of categorization. Rather, ITC neurons were sensitive to the physical appearance of the individual stimuli; its neurons did not “throw away” information about individuals in favor of the category groupings, like PFC [prefrontal cortex] neurons did. This finding suggests that learned visual categories are abstracted at the level of the PFC, not in visual cortex.
No, not really. Monkeys were able to easily learn visual categories when their lateral prefrontal cortices were ablated bilaterally, IF they were tested using an incentive value task (Minamimoto et al., 2010. Earlier single-unit recording studies (reviewed in the Miller 2007 chapter) required maintenance of a set of two stimulus-response mappings. Thus PFC might be necessary for rule-based response selection, but not for visual categorization.

Minamimoto T, Saunders RC, Richmond BJ (2010). Monkeys Quickly Learn and Generalize Visual Categories without Lateral Prefrontal Cortex. Neuron 66:501-507.

Categorization is a basic mental process that helps individuals distinguish among groups of negative and positive objects, e.g., poisons and nutrients, or predators and prey. Monkey experiments have suggested that lateral prefrontal cortex (LPFC) participates in learning and processing visual categories. However, in humans category specific visual agnosia follows inferior temporal cortex but not LPFC damage. Here, we use a new behavioral approach to show that both normal monkeys and those with bilateral removal of LPFC learn and generalize perceptual categories of related visual stimuli rapidly without explicit instruction. These results strongly indicate that visual categorization occurs at some earlier stage of feed-forward processing, presumably in temporal cortex, without top-down information from LPFC.

Minamimoto et al.'s incentive value task is shown below.

Figure 1 (A) Sequence of events during a trial of the reward-delay task. A visual cue (Cue) indicates size and delay interval for the reward after successful behavioral reaction (bar release within 200–3000 ms after green target appears).

You Are What You Eat, or Don't Eat

(2) Empathy and Diet? Are vegetarians too sensitive, or more empathetic? And those vegans, they're out of control!

Filippi M, Riccitelli G, Falini A, Di Salle F, Vuilleumier P, Comi G, Rocca MA (2010). The Brain Functional Networks Associated to Human and Animal Suffering Differ among Omnivores, Vegetarians and Vegans. PLoS ONE 5(5): e10847.

Empathy and affective appraisals for conspecifics are among the hallmarks of social interaction. Using functional MRI, we hypothesized that vegetarians and vegans, who made their feeding choice for ethical reasons, might show brain responses to conditions of suffering involving humans or animals different from omnivores. We recruited 20 omnivore subjects, 19 vegetarians, and 21 vegans. The groups were matched for sex and age. Brain activation was investigated using fMRI and an event-related design during observation of negative affective pictures of human beings and animals (showing mutilations, murdered people, human/animal threat, tortures, wounds, etc.). Participants saw negative-valence scenes related to humans and animals, alternating with natural landscapes. During human negative valence scenes, compared with omnivores, vegetarians and vegans had an increased recruitment of the anterior cingulate cortex (ACC) and inferior frontal gyrus (IFG). More critically, during animal negative valence scenes, they had decreased amygdala activation and increased activation of the lingual gyri, the left cuneus, the posterior cingulate cortex and several areas mainly located in the frontal lobes, including the ACC, the IFG and the middle frontal gyrus. Nonetheless, also substantial differences between vegetarians and vegans have been found responding to negative scenes. Vegetarians showed a selective recruitment of the right inferior parietal lobule during human negative scenes, and a prevailing activation of the ACC during animal negative scenes. Conversely, during animal negative scenes an increased activation of the inferior prefrontal cortex was observed in vegans. These results suggest that empathy toward non conspecifics has different neural representation among individuals with different feeding habits, perhaps reflecting different motivational factors and beliefs.

How did the authors get the idea for this experiment??

How Dare You! I Feel So Guilty! This Is an Outrage!

(3) Oh no! The neural correlates of "moral sentiments"? Smells like phrenology to me...

Green S, Ralph MA, Moll J, Stamatakis EA, Grafman J, Zahn R. Selective functional integration between anterior temporal and distinct fronto-mesolimbic regions during guilt and indignation. Neuroimage 2010 May 19. [Epub ahead of print].

It has been hypothesized that the experience of different moral sentiments such as guilt and indignation is underpinned by activation in temporal and fronto-mesolimbic regions and that functional integration between these regions is necessary for the differentiated experience of these moral sentiments. A recent fMRI study revealed that the right superior anterior temporal lobe (ATL) was activated irrespective of the context of moral feelings (guilt or indignation). This region has been associated with context-independent conceptual social knowledge which allows us to make fine-grained differentiations between qualities of social behaviours (e.g. "critical" and "faultfinding"). This knowledge is required to make emotional evaluations of social behaviour. In contrast to the context-independent activation of the ATL, there were context-dependent activations within different fronto-mesolimbic regions for guilt and indignation. However, it is unknown whether functional integration occurs between these regions and whether regional patterns of integration are distinctive for the experience of different moral sentiments. Here, we used fMRI and psychophysiological interaction analysis, an established measure of functional integration to investigate this issue. We found selective functional integration between the right superior ATL and a subgenual cingulate region during the experience of guilt and between the right superior ATL and the lateral orbitofrontal cortex for indignation. Our data provide the first evidence for functional integration of conceptual social knowledge representations in the right superior ATL with representations of different feeling contexts in fronto-mesolimbic regions. We speculate that this functional architecture allows for the conceptually differentiated experience of moral sentiments in healthy individuals.

Official Short Cuts Theatrical Trailer

Well, it looks like there was a winner after all, at least for tonight...

Minamimoto T, Saunders RC, Richmond BJ (2010). Monkeys Quickly Learn and Generalize Visual Categories without Lateral Prefrontal Cortex Neuron, 66 (4), 501-507 : 10.1016/j.neuron.2010.04.010

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