PSY100H1 Chapter Notes - Chapter 3: Choroid, Neocortex, Reticular Formation

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3 Feb 2013
PSYC31 Chapter 3: The Behavioral Geography of the Brain
New neurons are produced in some brain regions of adults in a number of mammalian species,
playing a role in brain injury repair, new learning, and maintenance of healthy neural functioning
Adult neurogenesis has been identified in the hippocampus and olfactory bulb in mammalian
brains and implicated in other limbic regions, in the neocortex, straitum, and substantia nigra
Neurogenesis in the hippocampus is thought to be especially critical for maintaining normal
cognition and emotional well-being
Basal ganglia and cerebellum are increasingly appreciated for their influences on cognition and
psychiatric disorders
Motor cortex appears to play an active role in processing abstract learned information
Strategically occurring lesions or abnormalities albeit small may nonetheless influence
neuropsychological functions
Brain Pathology and Psychological Function
any given behavior is the product of a myriad of complex neuropsychological and biochemical
interactions involving the whole brain
one focal lesion may affect many functions when the damaged neural structure is either a
pathway, nucleus, or region that is central in regulating or integrating a particular function
o these disruptions can produce a neurobehavioral syndrome (cluster of deficits that tend
to occur together with some regularity)
knowledge of the localization of dysfunction, the correlation between damaged
neuroanatomical structures and behavioral functions also enables neuropsychologists and
neurologists to make educated guesses about the site of a lesion on the basis of abnormal
patterns of behavior
similar lesions may have quite dissimilar behavioral outcomes
localization cannot imply a “push-button” relationship between local brain sites and specific
behaviors as the brain’s processing functions take place at multiple levels within complex
integrated, widely distributed systems
o lesions at many different brain sites may alter or extinguish a single complex act as can
lesions interrupting the neural pathways connecting areas of the brain involved in the
The Cellular Substrate
primary function of neuron is to provide network of connectivity between neurons and different
regions of the brain
brain connectivity is key to brain functioning
at birth, the full complement of neurons appears to be present, indicating an astonishing growth
pattern from conception to birth
glial cells (astrocytes) facilitate neural transmission and probably play a more direct role in
synaptic functioning and neural signaling
Glial cells serve as structural supports and also appear to have nutritional scavenger functions
and to release growth factors; additional role as a component in the BBB
Oligodendrocytes = form myelin for axonal insulation for high-speed conduction
Surface of dendrite may change in response to neural activity forming a spine
o Spine development is thought to be important in the formation of new memories and
neural plasticity
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Stimulation applied to neural pathway heightens that pathway’s sensitivity and increases the
efficacy with which neuronal excitation may be transmitted through synapse
Long-lasting synaptic modifications = long-term potentiation and long-term depression
o These are critical neurophysiological features of memory and learning
Each neurotransmitter can bind to and thus activate only those receptor sites with the
corresponding molecular conformation, but a single neuron may produce and release more than
one of these chemical messengers
When a circuit loses a sufficiently great number of neurons, the broken circuit can neither be
reactivated nor replaced
During development, some neurons initiate apoptosis which enhancing organization and
efficiency of specific neuronal pathways in a process called pruning
While apoptosis occurs normally in the development of the nervous system, some nervous
system diseases may result from apoptotic processes gone awry or other forms of cell deaths
which are normally prevented by neurotrophic factors
The Structure of the Brain
Embryological development has major anatomical divisions of the brain
o Hindbrain (pons, medulla, and cerebellum)
o Midbrain
o Forebrain (telencephalon and diencephalon)
The lowest brain centers are the most simply organized and mediate simpler and more primitive
Hemispheres mediate the highest levels of behavioral and cognitive function
Brain has 4 ventricles which have CSF running through them
CSF is also running between arachnoid membrane and dura mater (meninges)
CSF is produced in the choroid plexi
CSF is pressured in the ventricles, serving as a shock absorber and helping to maintain shape of
the soft nervous tissue of the brain by creating an outward pressure gradient that is held in
check by the mass of the brain
Blockage within the ventricular system affects CSF flow, producing obstructive hydrocephalus
o In disorders in which brain substance deteriorates the ventricles enlarge to fill the void
When vascular pathology occurs, its effects are typically associated with one or a combination of
the major blood vessels of the brain
It is in the intimate interaction between individual capillaries and neurons that neural function
or dysfunction occurs
It is the interplay between vascular damage and brain damage that gives rise to
neuropsychological impairments
3 major blood vessels of the brain
o Anterior cerebral (frontal lobe)
o Middle cerebral (lateral temporal, parietal and posterior frontal lobe)
o Posterior cerebral (brain stem and cerebellum)
Most frequent vascular source of neuropsychological deficits is associated with arterial side of
blood flow
The site of disease or damage to arterial circulation determines the area of the brain cut from its
oxygen and nutrients supply and to a large extent, the neuropathologic consequences of
vascular disease
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