Cognitive psychology is the study of mental activity as an information-processing problem. Cognitive
psychologists seek to identify the internal processing – the acquisition, storage, and use of information
– that underlies observable behavior.
2 key components underlying cognitive approach: (1) information processing depends on mental
representations, and (2) these mental representations undergo internal transformations.
Mental representations is thinking of an image, linguistic description, or mathematical formula when
considering a certain concept. Context helps to dictate which representational format is most useful.
Michael Posner (letter-matching task): this task is to evaluate whether both letters are vowels, both are
consonants, or one is a vowel and the other is a consonant.
Conditions: physical identity (AA), phonetic identity (Aa), same category (AU/SC), and
different category (AS).
Results: participants respond faster to the physical-identity condition, next fastest to the
phonetic-identity condition, and slowest to the same-category conditions. These results
suggest that we derive multiple representations of stimuli. We base one representation on the
physical aspects of the stimulus, a second representation corresponds to the letter’s identity,
and a third level of abstraction represents the category to which the letter belongs. This means
that physical representations are activated first, phonetic representations next, and category
representations last.
Internal transformation is when a sensory signal connects to with stored information in memory. E.g.,
an olfactory sensation that calls up a memory. In order to take action perceptual representations are
translated into action representations. Memory may alter the way we perceive something, and the way
information is processed is also influenced by attentional constraints.
Saul Sternberg (memory comparison task): in this task participants have to compare sensory
information with representations that are active in memory. The participant is presented with a set of
1, 2, or 4 letters and asked to memorize them. After a delay, a single probe letter appears, and the
participant indicates whether that letter was a member of the memory set. The participant engages in 4
primary mental operations: (1) encoding, (2) comparing, (3) deciding, and (4) responding.
Results: reaction time increases with set size, indicating that the target letter must be
compared with the memory set sequentially rather than in parallel.
(1) parallel process: the comparison process can be simultaneous for all items, reaction time
should be independent of the number of items in the memory set. (2) serial process: reaction
time should slow down as the memory set becomes larger, because more time is needed to
compare an item against a large memory list.
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Word superiority effect is the fact that participants are most accurate in identifying the target letter
when the stimulus is a word. Letters in words are reported more accurately than single letters and
letters embedded in non-words. This is an example of parallel processing.
The Stroop effect demonstrates the multiplicity of mental representation (color- and word
representation). A limitation is that the word-based representations are closely linked to the vocal
response system and have little effect when the responses are produced manually.
CHAPTER 3 SECTION 3.2
Using a population who has brain damage is a core method in cognitive neuroscience. It is important
to a clinical perspective to help design and evaluate rehabilitation programs.
A vascular disorder occurs when the brain is not getting enough oxygen and/or glucose. These two
molecules are essential for the cells to produce energy, fire action potentials, and make transmitters for
neuronal communication. Loss of oxygen for as little as 10 minutes can result in neuronal death.
Cerebral vascular accidents, or strokes, occur when there is a sudden disruption of the blood flow to
the brain. The most frequent cause is occlusion of the normal passage of blood by a foreign substance.
Atherosclerosis, which is the buildup of fatty acids, occurs in the arteries. When this buildup tissue
breaks free it becomes an embolus, which can get stuck in the artery. The ends of an artery divide in
capillaries. When there is a blockage of the artery, the brain region around the capillaries will become
dysfunctional because of the lack of oxygen and glucose, causing an infarct. An infarct is a small,
localized area of dead tissue.
A sudden drop in blood pressure may result blood from reaching the brain and a sudden rise in blood
pressure can cause an aneurysm. An aneurysm is a weak spot or distention in a blood vessel, to rupture
and hemorrhage. These are types of ischemia, which means inadequate blood supply.
A tumor, or neoplasm, is a mass of tissue that grows abnormally and has no physiological function.
They originate in glial cells and other supporting white matter tissues. Tumors that occur from gray
matter or neurons are not that common. Malignant (cancerous) tumors are often distributed over
several different areas and are more likely to recur after removal. The first concern is the location of
the tumor and not if it is benign or malignant.
Degenerative disorders are diseases in which the function or structure of the affected tissues or organs
changes for the worse over time. There are associated with both genetic aberrations and environmental
agents. The diagnosis is confirmed through a fMRI scan.
Viruses can also cause progressive neurological disorders. Viruses like HIV and AIDS can affect brain
areas.
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Traumatic brain injury is a form of acquired brain injury, occurs when a sudden trauma causes damage
to the brain. Damage can arise from the site of the blow, it can also occur at distant locations because
of the reactive forces that arise as the brain moves within and against the skull.
One consequence of the primary lesion from a TBI is edema (swelling) around the lesion. Limited
space within the skull causes an increase in the intracranial pressure (pressure of the ICF), in return
reducing the perfusion pressure (how much pressure it takes to push blood through the vessels) and
flow of blood throughout the brain, resulting in ischemia and, in some cases, the emergence of
secondary lesions.
A mild TBI or concussion may lead to chronic neurodegenerative consequences. Diffuse axonal injury
(DAI) is common with mTBI. This is the twisting, buckling, or distortion of the white matter that
occurs with an injury disrupts the axonal cytoskeleton and thus also axonal transport.
Epilepsy is a condition characterized by excessive and abnormally patterned activity in the brain
causing a seizure, a transient loss of consciousness. An electroencephalography (EEG) can confirm
seizure activity. Large-amplitude oscillations are seen.
Lesion studies have provided key insights into brain and behavior. Because if a neural structure
contributes to a task, then a structure that is dysfunctional should impair performance on that task.
Using CT- and MRI scans combined with tools that make analysis of the behavior deficits, comparing
healthy brains with injured brains, researchers have been able to link operations to specific brain area
underlying cognitive performance.
The challenge for a cognitive neuroscientist is to determine whether the observed behavioral problem
results from damage to a particular mental operation or is secondary to a more general disturbance,
because a brain injury can produce widespread changes in cognitive abilities.
Split-brain surgeries, or callosotomy, where fibers of the corpus callosum are severed, provided insight
into the roles of the two hemispheres on a wide range of cognitive tasks.
Lesions may result in the development of compensatory processes.
Single dissociation: when a lesion to brain area X impairs the ability of a patient to do task A but not
task B, then we can say that brain area X and task A are associated, whereas brain area X and task B
are dissociated.
Double dissociation: occurs when damage to area X impairs the ability to do task A but not task B, and
damage to are Y impairs the ability to do task B and not task A. The two areas have complementary
processing. E.g., damage to Wernicke’s area impairs comprehension but not the ability to speak
fluently.
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