Chapter 2 Review Questions

animal models (p. 31)

Broca’s aphasia; Wernicke’s aphasia (p. 33-34)

emergent property (p. 35)

corpus callosum; interhemispheric transfer (p. 34)

parallel; serial (p. 43)

Parallel processing implies the occurrence of simultaneous activity across multiple neural connections, whereas serial processing implies the occurrence of a single neural connection operating at a time. In the latter model, one process must be completed before the next process begins. (p. 43)

The interactionist perspective implies that the “mind” and “brain” are separate entities that have the capacity to influence each other and therefore both can exert causal control over each other. In contrast, the epiphenomenalist perspective implies that the mind is a mere “by-product” of brain activity, and as such has no causal influence over brain activity or behaviour. (p. 28-29)

By strategically positioning electrodes on the scalp, electrical activity from the brain can be recorded and translated into graphs. When this is repeated over many trials for the same cognitive task, average “waveform” patterns emerge in response to specific stimuli. These waveforms are called event-related potentials. They differ for different types of tasks. Interpreting their underlying cognitive processes is a challenging endeavour. Although ERPs can provide very high temporal resolution (on the order of a fraction of a second) they offer only limited spatial resolution (can localize only activity to large regions of the cortex). (p. 36)

Connectionism is an information-processing approach which models cognitive processes based on networks of connections among elementary units (called neurons). The strength of the connections among the neurons is dynamic, and the connectionist network “learns” by modifying the pattern of connection strengths so that the correct output (response) is achieved for any given input (stimulus). The connectionist approach differs from traditional information-processing approaches in that it attempts to model cognitive processes as they might actually be implement-ed by the networks of neurons in the brain. (pp. 42–43)

fMRI directly measures the local blood-oxygen content in the brain, which is an indirect measure of local brain activity. It provides far greater spatial resolution than ERP, so fMRI would be the more appropriate technique when activity needs to be localized to specific brain structures. (pp. 36, 38–40)

The law of mass action states that a cognitive function depends on a total mass of brain tissue, and the law of equipotentiality states that, to a certain extent, brain regions are unspecialized and functionally interchangeable. These two laws differ greatly from the perspective of strong localization of function, which asserts that specific regions of the brain perform specific, specialized functions. (p. 28)

The Hebb rule states that when neuron A repeatedly excites neuron B and causes it to fire regularly and persistently, then the connection between neurons A and B will be strengthened. Alternatively put, “neurons that fire together, wire together.” The Hebb rule provides a way for connections between neurons in a connectionist neural network to be modified and strengthened. (p. 42)

Parallelism views the mind and brain as two distinct aspects of a single reality. For every mental event experienced by an individual, there is a corresponding event that occurs in the brain. The emphasis is that mental events are reflected in brain events, and vice versa. Isomorphism implies a similar concept, except that it emphasizes the organization of brain events and mental events, as wholes. Perceptual information for the same external/physical stimulus can vary, giving rise to differing brain events that process each “version” of the external stimulus and result in different mental experiences of the stimulus. (pp. 29–30)

Sperry’s research on interhemispheric transfer demonstrates that communication between the brain’s hemispheres is enabled in large part by the corpus callosum. When the corpus callosum is severed, information transfer between the hemispheres is disrupted. Under these conditions, each hemisphere appeared to be “a separate mental domain operating with complete disregard—indeed with a complete lack of awareness—of what went on in the other. The split brain animal behaved . . . as if it had two entirely separate brains.” (pp. 34–35)

Phrenology was a nineteenth-century practice endorsed by Gall and Spurzheim, which embraced the idea of localization of function to the extreme. Localization of function conveys the notion that brain regions can be divided up into discrete locations that are responsible for specific types of cognitive processing. Phrenology aimed to “map” these regions of the brain by transcribing them off of the bumps located on a person’s skull. Whilst the concept of localization of function has found some merit in psychology, the idea that there is any correlation between bumps on a skull and cognitive traits has long since been abandoned. (p. 26)