Where in the brain is the self?

Localizing the self in the brain has been the goal of consciousness research for centuries. Recently, there has been an increase in attention to the localization of the self. Here we present data from patients suffering from a loss of self in an attempt to understand the neural correlates of consciousness. Focusing on delusional misidentification syndrome (DMS), we find that frontal regions, as well as the right hemisphere appear to play a significant role in DMS and DMS related disorders. These data are placed in the context of neuroimaging findings.     

What drives the organization of object knowledge in the brain?

Various forms of category-specificity have been described at both the cognitive and neural levels, inviting the inference that different semantic domains are processed by distinct, dedicated mechanisms. In this paper, we argue for an extension of a domain-specific interpretation to these phenomena that is based on network-level analyses of functional coupling among brain regions. On this view, domain-specificity in one region of the brain emerges because of innate connectivity with a network of regions that also process information about that domain. Recent findings are reviewed that converge with this framework, and a new direction is outlined for understanding the neural principles that shape the organization of conceptual knowledge.     

A general mechanism for decision-making in the human brain?

A new fMRI study by Heekeren and colleagues suggests that left dorsolateral prefrontal cortex (DLPFC) contains a region that integrates sensory evidence supporting perceptual decisions. DLPFC meets two criteria posited by Heekeren et al. for such a region: (1) its activity is correlated in time with the output of sensory areas of the visual cortex measured simultaneously, and (2) as expected of an integrator, its activity is greater on trials for which the sensory evidence is substantial than on trials for which the sensory evidence is weak. Complementary experiments in humans and monkeys now offer a realistic hope of elucidating decision-making networks in the primate brain.     

Does the brain calculate value?

How do people choose between options? At one extreme, the 'value-first' view is that the brain computes the value of different options and simply favours options with higher values. An intermediate position, taken by many psychological models of judgment and decision making, is that values are computed but that the resulting choices depend heavily on the context of available options. At the other extreme, the 'comparison-only' view argues that choice depends directly on comparisons, with or even without any intermediate computation of value. In this paper, we place past and current psychological and neuroscientific theories on this spectrum, and review empirical data that have led to an increasing focus on comparison rather than value as the driver of choice.     

Return of the mental image: are there really pictures in the brain?

In the past decade there has been renewed interest in the study of mental imagery. Emboldened by new findings from neuroscience, many people have revived the idea that mental imagery involves a special format of thought, one that is pictorial in nature. But the evidence and the arguments that exposed deep conceptual and empirical problems in the picture theory over the past 300 years have not gone away. I argue that the new evidence from neural imaging and clinical neuropsychology does little to justify this recidivism because it does not address the format of mental images. I also discuss some reasons why the picture theory is so resistant to counterarguments and suggest ways in which non-pictorial theories might account for the apparent spatial nature of images.     

Intervening in the psychopath’s brain

Psychopathy is a disorder involving personality and behavioral features associated with a high rate of violent aggression and recidivism. This paper explores potential psychopharmacological therapies to modulate dysfunctional neural pathways in psychopaths and reduce the incidence of their harmful behavior, as well as the ethical and legal implications of offering these therapies as an alternative to incarceration. It also considers whether forced psychopharmacological intervention in adults and children with psychopathic traits manifesting in violent behavior can be justified. More generally, the paper addresses the question of how to weigh the psychopath’s presumptive right to non-interference in his brain and mind against the public interest in avoiding harm.     

Is sexual-aggressive vocal communication related to asymmetric mechanisms in the brain?

In Mongolian gerbil males, a reliable asymmetric relationship has been discovered between a stereotyped ultrasonic vocalizattion and the volume of a discrete nucleus within the preoptic-anterior hypothalamic area, the sexually dimorphic area, pars compacta (SDApc). The steroid-sensitive ultrasonic, emitted at high levels during courtship interactions, is associated with the absence of aggressive encounters and appears to be necessary for the formation and maintenance of pair-bonds with females. Interactions between unfamilliar, non-pair-bonded adult male and estrous female gerbils result in male aggression, reduction of male ultrasonic calling, and disruption of normal female dartmale follow sociosexual sequences. Castration further reduces ultrasonic calling, inhibits normal sociosexual sequences, and increses aggression in interaction between unfamiliar compared to pair-bonded individuals. Bothg brain structure and lateralization of vocal function in males depend on the action of sex steroids during sexual differentiation and in adulthood. Thus, the gerbil provides a new model to study steroid-dependent lateralization of brain mechanisms of vocal behavior mediating aggressive-sexual relationships. © 1994 Wiley-Liss, Inc.     

Is the brain a memory box?

Bickle argues for both a narrow causal reductionism, and a broader ontological-explanatory reductionism. The former is more successful than the latter. I argue that the central and unsolved problem in Bickle's approach to reductionism involves the nature of psychological terms. Investigating why the broader reductionism fails indicates ways in which phenomenology remains more than a handmaiden of neuroscience.     

Does the brain prefer geometrical homogeneity?

Some patients with frontotemporal lobar degeneration (FTLD) have shown the development of painting or musical abilities after the onset of the disease. In this report, we present another emergent ability. A female patient with FTLD showing dense atrophy of the bilateral anterior lobes and a loss of voluntary activity in aspects of daily living, presented with the characteristic behaviours when given a paper and a pair of scissors. When a shape was already drawn on the paper, she showed reasonable skills with the scissors, cutting without any hesitation. When she cut a blank piece of paper, she showed quite unique geometrical preferences. Her severely degenerated brain combined with her geometrical abilities suggests that the human brain is naturally affected by geometrical homogeneity.     

Growth of white matter in the adolescent brain: Myelin or axon?

White matter occupies almost half of the human brain. It contains axons connecting spatially segregated modules and, as such, it is essential for the smooth flow of information in functional networks. Structural maturation of white matter continues during adolescence, as reflected in age-related changes in its volume, as well as in its microstructure. Here I review recent observations obtained with magnetic resonance imaging in typically developing adolescents and point out some of the known variations in structural properties of white matter vis-à-vis brain function in health and disease. I conclude by re-focusing the interpretations of MR-based studies of white matter from myelin to axon.     

Language switching in the bilingual brain: What’s next?

Recent work using functional neuroimaging with early bilinguals has found little evidence for separate neural systems for each language during picture naming (Hernandez, A. E., Dapretto, M., Mazziotta, J., & Bookheimer, S. (2001). Language switching and language representation in Spanish–English bilinguals: An fMRI study. Neuroimage, 14, 510–520). However, switching between languages in early bilinguals during picture naming shows increased activity in the Dorsolateral Prefrontal Cortex (DLPFC) suggesting the importance of maintaining goal related information in order to bias subsequent response selection (Braver, T. S., Barch, D. M., Kelley, W. M., Buckner, R. L., Cohen, N. J., Miezin, F. M., et al. (2001). Direct comparison of prefrontal cortex regions engaged by working and long-term memory tasks. Neuroimage, 14, 48–59; Cohen, J. D., Braver, T. S., & O’Reilly, R. C. (1996). A computational approach to prefrontal cortex, cognitive control and schizophrenia: Recent developments and current challenges. Philosophical Transactions of the Royal Society of London Series B-Biological Sciences, 351, 1515–1527; O’Reilly, R. C., Braver, T. S., & Cohen, J. D. (1999). A biologically based computational model of working memory. In E. Akira Miyake, E. Priti Shah & et al. (Eds.), Models of working memory: Mechanisms of active maintenance and executive control. (pp. 375–411): New York, NY, USA). The current study set out to test early bilinguals using a picture naming paradigm. Results revealed increased activity in the DLPFC and the superior parietal lobule during language switching compared to naming of pictures in a single language. Increased activity was also observed between early learned first and second languages. The results from single language conditions revealed differences in areas devoted to language processing such as the Superior Temporal Gyrus. However, increased activity in brain areas devoted to memory, somatosensory processing and emotion were also observed. Taken together these results replicate previous studies on language switching. They also extend studies on the neural bases of bilingualism by suggesting that early bilinguals’ representation of the two languages may be mediated by neural systems not typically associated with language. The article ends by considering future directions in understanding the brain bases of language switching and single language processing in bilinguals.     

Incongruent object/context relationships in visual scenes: Where are they processed in the brain?

Rapid object visual categorization in briefly flashed natural scenes is influenced by the surrounding context. The neural correlates underlying reduced categorization performance in response to incongruent object/context associations remain unclear and were investigated in the present study using fMRI. Participants were instructed to categorize objects in briefly presented scenes (exposure duration = 100 ms). Half of the scenes consisted of objects pasted in an expected (congruent) context, whereas for the other half, objects were embedded in incongruent contexts. Object categorization was more accurate and faster in congruent relative to incongruent scenes. Moreover, we found that the two types of scenes elicited different patterns of cerebral activation. In particular, the processing of incongruent scenes induced increased activations in the parahippocampal cortex, as well as in the right frontal cortex. This higher activity may indicate additional neural processing of the novel (non experienced) contextual associations that were inherent to the incongruent scenes. Moreover, our results suggest that the locus of object categorization impairment due to contextual incongruence is in the right anterior parahippocampal cortex. Indeed in this region activity was correlated with the reaction time increase observed with incongruent scenes. Representations for associations between objects and their usual context of appearance might be encoded in the right anterior parahippocampal cortex.