Online research in philosophy

The primrose path and prisoner's dilemma paradigms may require cognitive (executive) control: The active maintenance of context representations in lateral prefrontal cortex to provide top-down support for specific behaviors in the face of short delays or stronger response tendencies. This perspective suggests further tests of whether altruism is a type of self-control, including brain imaging, induced affect, and dual-task studies.

“The Matrix is a computer-generated dreamworld built to keep us under control” Morpheus, early in The Matrix. “ In dreaming, you are not only out of control, you don’t even know it…I was completely duped again and again the minute my pons, my amygdala, my perihippocampal cortex, my anterior cingulate, my visual association and parietal opercular cortices were revved up and my dorsolateral prefrontal cortex was muffled” ” J. Allan Hobson, The Dream Drugstore, p.64 The Matrix is an exercise in ambivalence, and at the very heart of that ambivalence lies the Dream. In our dreams, we are not in control. Real dreaming, unlike many popular philosophers’ fictions, is an altered state, closely related to the states induced by chemical manipulations such as the use of (certain) medical or recreational drugs. The dreaming brain is not like the wakeful brain. Normal sensory input is blocked, attentional capacities are impaired or lost, memory is distorted, reasoning and logic are weakened, narratives run wild, self-reflection is dampened or destroyed, emotion and instinct are hyperstimulated, and forms of ‘top-down’ willed control and decision-making diluted and easily overwhelmed.

Conscious perception, like the sight of a coffee cup, seems to involve the brain identifying a stimulus. But conscious input activates more brain regions than are needed to identify coffee cups and faces. It spreads beyond sensory cortex to frontoparietal association areas, which do not serve stimulus identification as such. What is the role of those regions? Parietal cortex support the ‘first person perspective’ on the visual world, unconsciously framing the visual object stream. Some prefrontal areas select and interpret conscious events for executive control. Such functions can be viewed as properties of the subject, rather than the object, of experience – the ‘observing self’ that appears to be needed to maintain the conscious state.

Rolls's proposal that the amygdala is critical for the association of visual objects with reward is not consistent with recent ablation evidence. Stimulus-reward association learning is more likely to depend on basal forebrain efferents to the inferior temporal cortex, some of which pass through the amygdala. It is more likely that the amygdala is involved in rapid modulation of stimulus reward value.

The current model, based on event-related potential (ERP) studies, posits that the working-memory system is a state of activated long-term memory; this appears comprehensive, but it needs further detailed analysis of functional neural connectivity analysis within the prefrontal cortex (PFC) and between the posterior and prefrontal cortex. Specifically, the role of dorsolateral PFC and anterior cingulate cortex (ACC) is probably critical for PFC's attentional controller. Neural implementation of the executive function in working memory appears critical to build a firm model.

Emotion is normally regulated in the human brain by a complex circuit consisting of the orbital frontal cortex, amygdala, anterior cingulate cortex, and several other interconnected regions. There are both genetic and environmental contributions to the structure and function of this circuitry. We posit that impulsive aggression and violence arise as a consequence of faulty emotion regulation. Indeed, the prefrontal cortex receives a major serotonergic projection, which is dysfunctional in individuals who show impulsive violence. Individuals vulnerable to faulty regulation of negative emotion are at risk for violence and aggression. Research on the neural circuitry of emotion regulation suggests new avenues of intervention for such at-risk populations.

William James presaged, and Alan Allport voiced criticisms of cause theories of executive attention for involving a homunculus who directs attention. I review discussions of this problem, and argue that existing philosophical denials of the problem depend on equivocations between different senses of “Cartesian error”. Another sort of denial tries to get around the problem by offering empirical evidence that such an executive attention director exists in prefrontal cortex. I argue that the evidence does not warrant the conclusion that an executive director can be localized in prefrontal cortex unless dubious assumptions are made, and that computational models purporting to support these assumptions either beg the question, or fail to model executive attention in terms of cause theories.

& Using functional magnetic resonance imaging, we examined whether individual differences in amygdala activation in response to negative relative to neutral information are related to differences in the speed with which such information is evaluated, the extent to which such differences are associated with medial prefrontal cortex function, and their relationship with measures of trait anxiety and psychological well-being (PWB). Results indicated that faster judgments of negative relative to neutral information were associated with increased left and right amygdala activation. In the prefrontal cortex, faster judgment time was associated with relative decreased activation in a cluster in the ventral anterior cingulate cor-.

The amygdala is a small subcortical structure that has long been implicated in the conditioning of fear and other emotions. It is heavily interconnected to a number of both cortical and subcortical structures and is thus well placed to integrate sensory inputs from multiple areas to produce emotional reactions directly as well as influence learning and attention systems. Data suggests that the amygdala works in close cooperation with the orbitofrontal cortex; the amygdala learns emotional reactions to stimuli, while the orbitofrontal cortex learns to inhibit the reactions from the amygdala in a context-sensitive manner. The hippocampus is encoding the contextual representations that are used by the orbitofrontal cortex. Being responsible for the conditioning of emotional reactions, the amygdala forms a part of a conceptual system integrating emotions, motivation and actions. The thesis briefly discusses this system, and also reviews the neurophysiological and neuroanatomical features of the amygdala, the orbitofrontal cortex and related areas. As a learning system, data suggests the amygdala is working as a classical conditioning system. This system is used both to elicit autonomous reactions to emotional stimuli directly through the central amygdala, and as an evaluative part of an instrumental conditioning system through the basolateral amygdala. Through this mechanism, the structure is also involved in selective memory consolidation and in selective priming of stimuli in the sensory cortices. Classical and instrumental conditioning is discussed, and a number of computational models of classical conditioning are presented and compared. The second half of the thesis presents a computational model of the amygdala and orbitofrontal cortex. The model has a very simple design for each component; much of the abilities of the model instead comes from the neuroanatomically guided interconnections between these components. The model is tested with only the amygdala and orbitofrontal cortex, and then extended with a simple hippocampal model able to generate contextual signals from an externally imposed attentional sequence. The model is compared to the previously tested conditioning models and its benefits and drawbacks - especially its current inability to handle time-dependent effects - are discussed.