The evolutionary forces that led to the unprecedented expansion of the human brain and the extreme cognitive prowess possessed by humans have always attracted a great deal of attention from the scientific community. Presented here is a novel theoretical perspective, where the driving force on human brain evolution was the need for enhanced ability to infer social values of conspecifics in the face of degradation and loss of chemosensory signalling mechanisms necessary for social communication present in most mammals. The lack of chemosensory communication of biologically relevant information between humans in the face of the need to make adaptive and accurate social evaluations, led to an exaption of mammalian chemosensory brain regions for the more complex task of inferring social values from behavioural cues that are variable, ambiguous, or otherwise difficult to detect and interpret. This change in social processing from perceptual evaluation to inferential computation placed a premium on cognitive capacity, thus selecting for larger more powerful brains. These selective processes would have left an indelible mark on the human brain, where the human homologues of regions involved in mammalian conspecific chemical communication, in particular the target regions of this study the amygdala and ventromedial prefrontal cortex (VMPC), should be involved in the processing of biologically relevant information and social inference. Several experiments were conducted to examine the role of these brain regions in social inferential processing using the lesion deficit method. First, given that conspecific chemical communication is particularly relevant for biologically imperative evaluation for the purposes of reproduction, VMPC and amygdala damage may result in abnormal mate-related decisions. Second, normal social attributions exhibit the correspondence bias, however damage to the target regions may result in an abnormal lack correspondence bias. Third, the current hypothesis is contrasted with another leading hypothesis, the Social Brain Hypothesis whose proponents predict a relationship between group-size and social cognition. Finally, if the target brain regions are truly integral in inferring social information, then damage to these regions will interfere with the ability to utilize transitive inference in social situations, and potentially in using transitive inference in general. Damage to the target areas produces limited effects on mate-related decisions and preferences. However, the current hypothesis may suggest that the target brain regions are only involved when the problem is inferential in nature rather than simpler perception of social information. In support of this notion, damage to the target regions results in a lack of the correspondence bias when making economic decisions. This alteration in social attributions actually leads to more `rational' decision-making in this context. In contrast to the predictions of the Social Brain Hypothesis, damage to the target regions produces no observed reduction in social group size, nor is there any observed relationship between perspective-taking ability and group size. Finally, damage to the VMPC produces deficits in using transitive inference in a non-social context perhaps hinting at the underlying computations of this region in inferring social information. In conclusion, it appears that the notion that the human brain regions that have been exapted from their duties in chemosensation and communication in mammalian brains has at least some validity. Moreover, these brain regions have been shifted by evolution to a more computationally complex process of social inference possibly providing the push toward larger and more powerful human brains.

Decision-making in the context of leadership, has received scant attention in the management literature, which has traditionally centered on general mental ability and personality as predictors of effectiveness. This research effort bridges the neuroscientific and management literatures to offer an alternative, neuropsychological profile of effective leadership by proposing prefrontal brain processes (executive function) as a key component and predictor of complex decision-making and leadership effectiveness. While the management literature has largely viewed decision-making as a cognitive ability, neuroscience informs us that this complex function emerges from the integration of affective and cognitive signals in the prefrontal cortex. In an attempt to identify the neural predictors of effective leadership decision-making, 105 corporate leaders were assessed on a robust array of neuropsychological indices of prefrontal brain function. These were in turn correlated with their leadership and decision-making abilities after controlling for general mental ability and personality, utilizing structural equation modeling. Executive function incrementally predicts complex decision-making and transformational leadership effectiveness, above and beyond general mental ability. Complex decision-making does not appear to be central to leadership effectiveness, while extraversion emerges as the strongest predictor of transformational leadership followed by executive function. Executive function, extraversion and general mental ability do not predict transactional leadership. These results would need replication in a larger dataset to establish their validity, especially in the case of executive function. While the heritability of leadership ability has emerged as fairly significant, this opens the field to unearthing the biological variables and predictors of leadership ability. Neuroscience thus has the potential to offer biomarkers and metrics of leadership that can further not only our foundational knowledge of organizational behavior, but can also find useful applications in recruitment, training and development practice, though this cross-disciplinary initiative is in its infancy. Based on the preliminary results from this study, executive function (which has so far remained in the domain of neurology) has the potential to inform and measure leadership effectiveness.

Detecting and interpreting sensory events, and remembering those events in in the service of future actions, forms the foundation of all behavior. Each of these pillars of the so-called "perception-action cycle" have been topics of extensive inquiry throughout recorded history, with philosophical foundations provided by early BCE and CE periods (especially during the Classic and Renaissance eras) leading to intensive empirical study in the twentieth and twenty-first centuries. Such experiments have described detailed (but incomplete) behavioral functions reflecting perception and memory, and have begun to unravel the extraordinarily complex substrates of these functions in the nervous system. The current dissertation was motivated by these findings, with the goal of meaningfully extending our understanding of such processes through a multi-experiment approach spanning the behavioral and neurophysiological levels. The focus of these experiments is on short-term memory (STM), though as we shall see, STM is ultimately inseparable from sensory perception and is directly or indirectly associated with guidance of motor responses. It thus provides a nexus between the sensory inputs and motor outputs that describe interactions between the organism and environment. In Chapter 2, previous findings from nonhuman primate literature describing relatively poor performance for auditory compared to visual or tactile STM inspired similar comparisons among modalities in humans. In both STM and recognition memory paradigms, accuracy is shown to be lowest for the auditory modality, suggesting commonalities among primate species. Chapters 3-5 examined STM processing in nonhuman primates at the behavioral and neurophysiological levels. In Chapter 3, a systematic investigation of memory errors produced by recycling memoranda across trials (proactive interference) is provided for the understudied auditory modality in monkeys. Such errors were ameliorated (but not completely eliminated) by increasing the proportions of unique memoranda presented within a session, and by separating successive trials by greater time intervals. In Chapter 4, previous results revealing a human memory advantage for audiovisual events (compared to unimodal auditory or visual events) inspired a similar comparison in monkeys using a concurrent auditory, visual, and audiovisual STM task. Here, the primary results conformed to a priori expectations, with superior performance observed on audiovisual trials compared to either unimodal trial type. Surprisingly, two of three subjects exhibited superior unimodal performance on auditory trials. This result contrasts with previous results in nonhuman primates, but can be interpreted in light of these subjects' extensive prior experience with unimodal auditory STM tasks. In Chapter 5, the same subjects performed the concurrent audiovisual STM task while activity of single cells and local cell populations was recorded within prefrontal cortex (PFC), a region known to exhibit multisensory integrative and memory functions. The results indicate that both of these functions converge within PFC, down to the level of individual cells, as evidenced by audiovisual integrative responses within mnemonic processes such as delay-related changes in activity and detection of repeated versus different sensory cues. Further, a disproportionate number of the recorded units exhibited such mnemonic processes on audiovisual trials, a finding that corresponds to the superior behavioral performance on these trials. Taken together, these findings reinforce the important role of PFC in STM and multisensory integration. They further strengthen the evidence that "memory" is not a unitary phenomenon, but can be seen as the outcome of processing within and among multiple subsystems, with substantial areas of overlap and separation across modalities. Finally, cross-species comparisons reveal substantial similarities in memory processing between humans and nonhuman primates, suggesting shared evolutionary heritage of systems underlying the perception-action cycle.

Dehumanization is a process whereby people fail to view others as human beings. Instead, the others are perceived as nonhuman animals or objects, unworthy of the same moral treatment. Dehumanization has previously been studied in a variety of different scholarly domains without adhering to a uniform theoretical framework. This literature review contrasts research on fully humanized perception, with research on dehumanized perception, and proposes neural areas which are likely to be involved. Not every aspect of dehumanization can be understood at the neurological level. To understand what factors lead up to, and modulates dehumanization, other perspectives might also be necessary. Dehumanized perception is coupled with reduced activity in the social cognitive brain network, a wide network which encompasses several cortical and subcortical areas. This disengages prosocial abilities and allows for other people to be treated like objects and means to an end. One area of special interest is the medial prefrontal cortex (MPFC). It functions as an integration center in the person perception network and is also active when we make moral judgments, empathize, or take the perspective of someone else. For this reason, the MPFC is sometimes used as an index of dehumanized perception.

Previous research indicates that many important changes in executive functions, or higher cognitive capacities, occur between the ages of three and five years. Additionally, a distinction can be made between the cognitive functions associated with two different cortical regions. The functions of the dorsolateral prefrontal cortex (DL-PFC) are assessed using 'cool' tasks that are abstract and decontextualised. In contrast, the functions of the orbitofrontal cortex (OFC) are assessed using 'hot' tasks that require flexible appraisal of the affective significance of stimuli (Zelazo & Müller, 2002). Different clinical populations have been hypothesized to differ in terms of their impairment on tasks associated with each area of functioning. Current research conclusions regarding the primacy of hot versus cool executive function impairments are limited, however, as they have not taken complexity into account. That is, tasks currently used in investigations of hot and cool executive functions might differ in terms of the complexity of the cognitive processes that the tasks require. Therefore, comparisons across tasks may be misleading because these tasks vary in terms of the demands they place on participants as well as their hot versus cool status. While complexity theories have been applied to a number of cool tasks, only one hot task, those measuring theory-of-mind abilities, have been analysed in terms of complexity. One aim of the current research was to modify several tasks presumed to measure OFC performance to include a complexity manipulation. Tasks from three hot domains (conditional discrimination, the Children's Gambling Task, and future-oriented decision-making) were analysed in terms of their relational complexity, that is, the number of related entities or arguments inherent in a task or concept (Halford, 1993). Based on these complexity analyses, binary-relational and ternary-relational items of each of these tasks were developed or existing tasks were selected and/or modified. The binary-relational items were closely matched to the ternary-relational items in terms of stimuli and procedure, however, they were lower in complexity. After pilot testing, the three new measures of hot executive functioning were included in a larger test battery that was administered to a sample of 120 normally developing 3-, 4-, 5- and 6-year-old children. Existing binary- and ternary-relational items assessing theory-of-mind (a hot task) and three cool measures (transitivity, class inclusion and the Dimensional Change Card Sort test) were also included. The inclusion of measures of both hot and cool executive functions, each with complexity manipulated, allowed for the examination of a possible differential age of emergence of executive abilities associated with the DL-PFC versus the OFC. In support of the relational complexity approach, significant complexity effects were found across all seven tasks. Items at a higher level of complexity were experienced as relatively more difficult by children of all ages. Significant effects of age were also observed, with performance across all tasks increasing with age. The age effects were strongest on the ternary-relational items. The pass-fail data indicated that the majority of children in all age groups succeeded on the binary-relational items. However, it was not until a median of five years of age that children were able to process ternary relations. Consequently, the ternary-relational items produce the greatest differences in performance between the four age groups. The overall pattern of the results also suggested that a distinction can be made between the ages of emergence of abilities associated with the OFC versus the DL-PFC. The results of the pass-fail percentages, patterns of age-related change and age effects on domain factor scores all suggested that while hot executive functions may begin to develop around four years of age, similar levels of improvement are not seen in cool executive functions until five years of age. Thus, the ability to succeed on ternary-relational items of hot executive function tasks appeared to emerge slightly earlier than the cool executive function tasks. Complexity appears to be a critical factor underlying children's performance on executive function tasks, and future assessment regarding the development of executive abilities will benefit from keeping this in mind. While some refinement of new task items may be beneficial, the current test battery may have utility in further examinations of the executive profiles underlying clinical groups, such as children with autism and ADHD.

<p>Although consciousness has been studied since ancient time, how the brain implements consciousness is still considered a great mystery by most. This thesis investigates the neural correlates of consciousness by measuring brain activity with functional magnetic resonance imaging (fMRI) while specific contents of consciousness are defined and maintained in various experimental settings. Study 1 showed that the brain works differently when creating a new conscious percept compared to when maintaining the same percept over time. Specifically, sensory and fronto-parietal regions were activated for both conditions but with different activation patterns within these regions. This distinction between creating and maintaining a conscious percept was further supported by Study 2, which in addition showed that there are both differences and similarities in how the brain works when defining a visual compared to an auditory percept. In particular, frontal cortex was commonly activated while posterior cortical activity was modality specific. Study 3 showed that task difficulty influenced the degree of frontal and parietal cortex involvement, such that fronto-parietal activity decreased as a function of ease of identification. This is interpreted as evidence of the non-necessity of these regions for conscious perception in situations where the stimuli are distinct and apparent. Based on these results a model is proposed where sensory regions interact with controlling regions to enable conscious perception. The amount and type of required interaction depend on stimuli and task characteristics, to the extent that higher-order cortical involvement may not be required at all for easily recognizable stimuli.</p>

Normal aging is associated with a decline in different cognitive domains and local structural atrophy as well as decreases in dopamine concentration and receptor density. To date, it is largely unknown how these reductions in dopaminergic neurotransmission affect human brain regions responsible for reward-based decision making in older adults. Using a learning criterion in a probabilistic object reversal task, we found a learning stage by age interaction in the dorsolateral prefrontal cortex (dIPFC) during decision making. While young adults recruited the dlPFC in an early stage of learning reward associations, older adults recruited the dlPFC when reward associations had already been learned. Furthermore, we found a reduced change in ventral striatal BOLD signal in older as compared to younger adults in response to high probability rewards. Our data are in line with behavioral evidence that older adults show altered stimulus-reward learning and support the view of an altered fronto-striatal interaction during reward-based decision making in old age, which contributes to prolonged learning of reward associations.

Although consciousness has been studied since ancient time, how the brain implements consciousness is still considered a great mystery by most. This thesis investigates the neural correlates of consciousness by measuring brain activity with functional magnetic resonance imaging (fMRI) while specific contents of consciousness are defined and maintained in various experimental settings. Study 1 showed that the brain works differently when creating a new conscious percept compared to when maintaining the same percept over time. Specifically, sensory and fronto-parietal regions were activated for both conditions but with different activation patterns within these regions. This distinction between creating and maintaining a conscious percept was further supported by Study 2, which in addition showed that there are both differences and similarities in how the brain works when defining a visual compared to an auditory percept. In particular, frontal cortex was commonly activated while posterior cortical activity was modality specific. Study 3 showed that task difficulty influenced the degree of frontal and parietal cortex involvement, such that fronto-parietal activity decreased as a function of ease of identification. This is interpreted as evidence of the non-necessity of these regions for conscious perception in situations where the stimuli are distinct and apparent. Based on these results a model is proposed where sensory regions interact with controlling regions to enable conscious perception. The amount and type of required interaction depend on stimuli and task characteristics, to the extent that higher-order cortical involvement may not be required at all for easily recognizable stimuli.

Near-infrared spectroscopy (NIRS) in an imaging technique that has gained much attention in brain-computer interfaces (BCIs). Previous NIRS-BCI studies have primarily employed temporal features, derived from the time course of hemodynamic activity, despite potential value contained in the spatial attributes of a response. In an initial offline study, we investigated the value of using joint spatial-temporal pattern classification with dynamic NIR topograms to differentiate intentional cortical activation from rest. With the inclusion of spatiotemporal features, we demonstrated a significant increase in achievable classification accuracies from those obtained using temporal features alone (p < 10-4). In a second study, we evaluated the feasibility of implementing joint spatial-temporal pattern classification in an online system. We developed an online system-paced NIRS-BCI, and were able to differentiate two cortical states with high accuracy (77.4±10.5%). Collectively, these findings demonstrate the value of including spatiotemporal features in the classification of functional NIRS data for BCI applications.

Consolidation of associative memories may depend on communication between the lateral entorhinal cortex (LEC) and hippocampus (HPC) for recently learned memories and the LEC and medial prefrontal cortex (mPFC) for remote memories. To determine whether direct connections between these regions are necessary for the retrieval of a recently or remotely learned memory, rats acquired an associative memory through trace eyeblink conditioning and were tested for memory retention after inactivating the regions of interest with the GABAA agonist, muscimol. Inactivating the LEC-HPC connection did not impair memory retrieval. However, inactivating the LEC-mPFC connection impaired remote, but not recent, memory retrieval. Thus, the LEC and mPFC connection is necessary for the retrieval of a remotely, but not recently learned associative memory. Increased reliance on the entorhinal-prefrontal connection indicates the strengthening of functional connectivity between the two regions, which may be a biological correlate for the proposed reorganization during systems consolidation.