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Decoding the neural substrates of reward-related decision making with functional MRI.: Proceedings of the National Academy of Sciences of the USA A, Vol. 104, No. 4. (23 January 2007), pp. 1377-1382.Alth ough previous studies have implicated a diverse set of brain regions in reward-related decision making, it is not yet known which of these regions contain information that directly reflects a decision. Here, we measured brain activity using functional MRI in a group of subjects while they performed a simple reward-based decision-makin g task: probabilistic reversal-learn ing. We recorded brain activity from nine distinct regions of interest previously implicated in decision making and separated out local spatially distributed signals in each region from global differences in signal. Using a multivariate analysis approach, we determined the extent to which global and local signals could be used to decode subjects' subsequent behavioral choice, based on their brain activity on the preceding trial. We found that subjects' decisions could be decoded to a high level of accuracy on the basis of both local and global signals even before they were required to make a choice, and even before they knew which physical action would be required. Furthermore, the combined signals from three specific brain areas (anterior cingulate cortex, medial prefrontal cortex, and ventral striatum) were found to provide all of the information sufficient to decode subjects' decisions out of all of the regions we studied. These findings implicate a specific network of regions in encoding information relevant to subsequent behavioral choice.AN Hampton, JP O'Doherty

Source: Proceedings of the National Academy of Sciences of the USA A, Vol. 104, No. 4. (23 January 2007), pp. 1377-1382.
Dorsolateral prefrontal and anterior cingulate cortex volumetric abnormalities in adults with attention-defi cit/hyperactiv ity disorder identified by magnetic resonance imaging.: Biol Psychiatry, Vol. 60, No. 10. (15 November 2006), pp. 1071-1080.OBJE CTIVES: Gray and white matter volume deficits have been reported in a number of studies of children with attention-defi cit/hyperactiv ity disorder (ADHD); however, there is a paucity of structural magnetic resonance imaging (MRI) studies of adults with ADHD. This structural MRI study used an a priori region of interest approach. METHODS: Twenty-four adults with DSM-IV ADHD and 18 healthy controls comparable on age, socioeconomic status, sex, handedness, education, IQ, and achievement test performance had an MRI on a 1.5T Siemens scanner. Cortical and sub-cortical gray and white matter were segmented. Image parcellation divided the neocortex into 48 gyral-based units per hemisphere. Based on a priori hypotheses we focused on prefrontal, anterior cingulate cortex (ACC) and overall gray matter volumes. General linear analyses of the volumes of brain regions, adjusting for age, sex, and total cerebral volumes, were used to compare groups. RESULTS: Relative to controls, ADHD adults had significantly smaller overall cortical gray matter, prefrontal and ACC volumes. CONCLUSIONS: Adults with ADHD have volume differences in brain regions in areas involved in attention and executive control. These data, largely consistent with studies of children, support the idea that adults with ADHD have a valid disorder with persistent biological features.LJ Seidman, EM Valera, N Makris, MC Monuteaux, DL Boriel, K Kelkar, DN Kennedy, VS Caviness, G Bush, M Aleardi, SV Faraone, J Biederman

Source: Biol Psychiatry, Vol. 60, No. 10. (15 November 2006), pp. 1071-1080.
Protostylid variation in Australopithec us: Journal of Human Evolution, Vol. 46, No. 5. (May 2004), pp. 579-594.Recent advances in computed tomography (CT) and genetics provide new insights into the morphology and biology of anatomical traits, particularly in the dentition. As we move towards a fuller understanding of the genetic and developmental bases for dental traits, we need to reassess the taxonomic and evolutionary variation of established characters. Quantitative genetic analyses indicate that the degree of expression of upper and lower primate cingular remnants are genetically interdependent . This has serious evolutionary implications that need to be explored for fossil hominids. Studies of Carabelli's cusp, a cingular remnant on hominid upper molars, have been advanced through both genetic and CT analyses setting the stage for such an investigation. But its mandibular morphological homologue, the protostylid has not been similarly studied. This paper represents the first step towards a quantitative understanding of the variation and evolution of this trait in early hominids. Since the first discoveries of Australopithec us specimens in South Africa more than sixty years ago, cingular features on lower molars have played a significant role in the description and comparison of hominid taxa. This largely qualitative history is reviewed. Because the modern human classification system for protostylid variation does not adequately describe the variation seen in Australopithec us samples, a quantification scheme with six expression states is established. Using this new protocol, protostylid variation in six species of Australopithec us is assessed. Results from these analyses show that the distribution of the degree of protostylid expression in these species is highly varied. When first, second, and third molar samples are considered separately, the distribution of expression states is found to differ considerably within the same species. These results provide a foundation for further genetic and developmental research on the evolutionary history of the hominid dentition.Lesl ea Hlusko

Source: Journal of Human Evolution, Vol. 46, No. 5. (May 2004), pp. 579-594.

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