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Chapter Six. The Neuroscience Approach: Mind As Brain. Neuroscience. The study of nervous system anatomy and physiology in man and other species. Cognitive neuroscience studies the structures and processes underlying cognitive function.

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Chapter Six

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Chapter six

Chapter Six

The Neuroscience Approach: Mind As Brain


Neuroscience

Neuroscience

  • The study of nervous system anatomy and physiology in man and other species.

  • Cognitive neuroscience studies the structures and processes underlying cognitive function.

  • What are the neural mechanisms for pattern recognition, attention, memory, and problem solving?


Neuroscience methods

Neuroscience methods

In brain damage techniques investigators study the effects of accidental or deliberate nervous- system damage. There are two types:

  • The case study method looks at the effects of brain damage due to stroke, head trauma, or other injury in humans.

  • In lesion studies, an electrode is used to selectively destroy a specific brain area of an animal. The resulting behavioral deficits are then examined.


Brain recording techniques

Brain recording techniques

  • The brain’s electrical activity can be measured in a variety of ways.

  • In single-cell recording an electrode is inserted into or adjacent to a neuron.

  • In multiple-unit recording, a larger electrode is used to measure the activity of a group of neurons.


Brain recording techniques1

Brain recording techniques

  • An electroencephalogram (EEG) provides an even broader view of brain action. Electrodes placed on the scalp measure the gross electrical activity of the entire brain.

  • An EEG recording in response to the presentation of a stimulus is an event-related potential.


Brain imaging

Brain imaging

  • Recent years have seen the introduction of more sophisticated devices.

  • Computer Axial Tomography (CAT). X-rays passed through the brain from different perspectives are used to construct 2-D and 3-D images.

  • Positron Emission Tomography (PET). Radioactively tagged glucose molecules used to measure which brain areas are most active.


Brain imaging1

Brain imaging

  • In magnetic resonance imaging (MRI) soft tissue structure is measured by the alignment of protons within a powerful magnet.

  • Functional magnetic resonance imaging (fMRI) is a version that shows changes in brain activity over time.


Electrical stimulation

Electrical stimulation

  • In this procedure neurons are electrically stimulated and the resulting behavior is studied.

  • Involves activation of brain areas rather than their destruction or passive measurement.


Anatomy of a neuron

Anatomy of a neuron


Anatomy of a synapse

Anatomy of a synapse


The cortex

The cortex


Visual pathways

Visual pathways


Visual agnosias

Visual agnosias

  • A visual agnosia is an inability to recognize a visual object. There are two categories:

  • Apperceptive agnosia. Difficulty in assembling the pieces or features of an object together into a meaningful whole.

  • Associative agnosia. Can perceive a whole object but have difficulty naming or assigning a label to it.


Prosopagnosia

Prosopagnosia

  • Prosopagnosia is another type of agnosia in which patients have difficulty recognizing faces.

  • In humans, cells that respond to faces are found in the fusiform face area (FFA) located in the temporal lobe.


Neural models of attention

Neural models of attention

  • In this component process model of attention, different brain areas perform distinct functions (Posner, et. al., 1987).

  • Parietal lobe disengages attention from a fixed position.

  • Superior colliculus moves attention to a new location.

  • Thalamus engages attention at the new position.


Neural models of attention1

Neural models of attention

  • In this distributed network model (Mesulam, 1981) the brain areas subsuming attention are redundant and can perform multiple functions.

  • Posterior parietal cortex provides a sensory map of space to which attention is directed.

  • Cingulate cortex determines what is important to pay attention to and what can be ignored.

  • Frontal cortex coordinates motor programs.

  • Reticular structures generate arousal and vigilance levels.


Neuroscience of memory

Neuroscience of memory

  • Karl Lashley (1950) searched for the engram, the physical location of a memory.

  • He destroyed progressively larger areas of monkey brain tissue after training them on a task.

  • The monkeys retained the memory, suggesting it was distributed to many parts of the brain, a principle known as equipotentiality.


Learning and memory

Learning and memory

  • Learning is a change in the nervous system caused by some event that in turn causes a change in behavior.

  • Learning in a nervous system requires a change in the structure or biochemistry of a synapse, what is called synaptic plasticity.

  • If a group of neurons is repeatedly activated, the synaptic connections between them will be strengthened. This circuit will then contain the new information.


The hippocampus

The hippocampus

  • This brain structure is responsible for consolidation, the transfer of information from STM to LTM.

  • Damage to the hippocampus results in anterograde amnesia, an inability to retain new information subsequent to the damage. Example: The tragic case of H.M.

  • This should be distinguished from retrograde amnesia, in which it is difficult to remember information learned prior to a traumatic incident.


Hippocampal structure and function

Hippocampal structure and function


Neural substrates of working memory

Neural substrates of working memory

  • Storage of verbal material: posterior parietal cortex in left hemisphere.

  • Rehearsal of verbal material: prefrontal cortex.

  • Storage of spatial information: posterior parietal cortex in right hemisphere.

  • Maintenance of spatial information: dorsolateral prefrontal cortex.


Neural substrates of long term memory

Neural substrates of long-term memory

  • Semantic memory linked to the limbic cortex.

  • Consolidation of episodic memory mediated by the hippocampus.

  • Procedural memory function associated with basal ganglia and motor cortex.


Neuroscience of problem solving

Neuroscience of problem solving

  • Patients with executive dysfunction have difficulty starting and stopping behaviors and in problem solving. They suffer frontal lobe damage.

  • They may also be impelled to engage in a behavior triggered by a stimulus. This is called environmental dependency syndrome. Example: seeing a pen causes them to pick it up and start writing.


The tower of london problem

The Tower of London problem

  • Left anterior frontal lobe damage seems to underlie planning and sequencing in this task (Shallice, 1982).


Theories of executive function

Theories of executive function

  • Executive function refers to the cognitive operations used in problem solving. They include planning, sequencing of behavior, and goal attainment.

  • Automatic attentional processes do not require conscious control. They are triggered by environmental stimuli.

  • Controlled attentional processes require conscious control. Made in response to novel or difficult situations.


Theories of executive function1

Theories of executive function

  • In the Norman-Shallice (1980) model, action schemas are activated by stimuli or other schemas and produce a behavior.

  • Action schemas are like scripts in that they specify what to do in a specific situation. They control automatic attentional processes.

  • Action schemas inhibit one another so that multiple actions are not executed simultaneously. Called contention scheduling.

  • This system works well for routine familiar tasks.


Theories of executive function2

Theories of executive function

  • But for new or difficult problem solving situations for which there is no known solution, another system is needed.

  • The Supervisory Attentional System (SAS) has more general flexible strategies that can be applied to any problem situation.

  • The SAS monitors schemas and can suppress or turn off inappropriate ones.

  • Probable neural location is the left anterior frontal lobe.


Theories of executive function3

Theories of executive function

  • Stuss and Benson (1986) propose an alternate model with three levels:

    • Lowest level governs automatic responses. Location: posterior brain areas.

    • Intermediate supervisory level runs executive processes and solves problems. Location: frontal lobe.

    • Highest level is metacognitive. It monitors and regulates any aspect of cognition. Location: prefrontal cortex.


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