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Brain Week 5 ([H16] What happens when the brain misbehaves? (Research…
Brain Week 5
[H16] What happens when the brain misbehaves?
Genetic, biochemical, anatomical & social-environmental variables.
Disease
Classification
Epidemiology
The study of the emergence of diseases
DSM
(Diagnostical and Statictical Manual of mental disorders)
The American Psychiatric Association’s classification system for
psychiatric disorders
#
Classify by difference shown from Imaging
Not much used as of this moment - techniques got to have higher sensitivity & specificity
Treatment types
Neurosugeries
Opening up the skull and performing sugery on brain tissue
For example in stemcel implantations,
Deep Brain Stimulation
(DBS) and brain tissue removal/reparation
#
Electrophysiology
Stimulating the brain through the skull
For example in ECT and TMS (transcranial magnetic stimulation)
Farmacological
Inserting chemicals that have influence on the brain
For example drugs or antibiotics (Neuroleptica is tused for schizofrenie, axiolytica for anxiety, SSRI's for depression, L-dopa for Parkinson's disease)
Behavioral
Treatment in which the body gets manipulated
For example behavioral therapy, psychotherapy, cognitive-behavioral therapy,
virtual reality simulation
Virtual Reality Simulation
is a controlled, virtual-immersion environment that, by allowing individuals to relive traumatic events, gradually desensitizes them to stress. Also helps with fighting different
phobias
and and other forms of
anxieties
.
Research challenges
Organizational complexity
: complex nervous system, wide variety of cell types in brain, connections are plastic.
Systemic complexity
: multiple receptor systems serve many different functions.
Neuronal plasticity
: impossible to tie dopamine depletion to a consistent behavioral syndrome (in Parkinson’s disease)
Compensatory plasticity
: even the best technology produces uncertain relationships. People can change their behavior to adapt to neural change, and they can display abnormal behavior without obvious brain pathology.
Technological resolution
: lack the detail to detect subtle neuronal change.
Modelling simplicity
: animal models lead to advances in understanding of neural conditions and their treatments. Oversimplified however.
Modelling limitations
: caution to psychiatric disorders in which causes are still unknown if cure is reportedly found. Many symptoms of disorders are largely cognitive. Objectively identifying any cognitive processes mimicked by a laboratory model is difficult.
Neurology
is related to brain disorders
Psychiatry
is related to behavioral disorders
Causes of
brain disorders
are relatively better known, therefore easier to indicate them
Loss of neural function and connections
seen in disorders such as multiple sclerosis and myasthenia gravis
Multiple Sclerosis
: degrading myelin in the central nervous system. Motoric system neurons get damaged this way. Cause can be an escalated reaction against a virus in the auto immune system. No cure available yet
Rapid cell death
, as in stroke or traumatic brain injury
Traumatic brain injury
is not innate, the damage can cause stop the brains blood supply, or give infections. You can get shortterm or longterm loss of consciousness
Ideal treatment is dissolving blood clot and so restoring the blood supply
before
damage is done
Stroke
is a cerebral infarction which can cause brain tissue to die out due to
ischemia
(blood shortage).
Progressive cell death
resulting from neurodegenerative causes, as in Parkinson’s or Alzheimer’s disease
Cause
Parkinson's
disease = degeneration in the substantia nigra & not enough dopamine. Treatments are in the form of L-dop,
DBS
and
stemcel transplantation
#
Epigenetic
mechanisms at work prenatally, later in life, even in succeeding generations
Genetic errors
, as in Huntington’s disease
Causes of
behavioral disorders
are relatively less known, compared to brain disorders.
Example of a behavioral disorder
is Phenylketonuria
(PKU)
Caused by high levels of the aminoacid
Phenylalanine
in the blood, because of a
defect gene
responsible for the enzyme called "Phenylalanine hydroxylase that turns phenylalanine into tyrosine. The aminoacid now accumulates in the liver, which then can cause mental disorder, and a low IQ.
For this reason diagnosing behavioral disorders is somewhat trickier (judging behavior objectively is hard and the ones giving treatments can have a prejudice, which can bias the symptom information they receive, and also specific behavior doesn't have to link to specific brain areas)
Animal models are handy in this case, but they're generally oversimplified models
#
Another example is
Schizofrenia
Symptoms are hallucinations and unlogical thought patterns. Deviation in the prefrontal and temporal cortex. Like many other psychiatric disorders, its hard to treat.
[H12] What causes Emotional and motivated behaviour?
Behaviour for brain maintainance
The brain needs stimulation (
Sensory deprivation
: Experimental setup in which a subject is allowed only restricted sensory input; subjects generally have a low tolerance for deprivation and may even display hallucinations.)
Some behaviours are rewarding,
There are neural circuits for reward
Androgen
: Male hormone related to level of sexual interest. High levels, high interest. In absence of androgens, the brain circuits are still present but more difficult to activate.
For instance: Cat killing prey is rewarding
Chemical senses
Olfactory epithelium
Air enters our nose and goes to the olfactory mucosa. Here the odorant molecules bind to cilia of the olfactory receptor that responds to that odor (each receptor responds to a range of odors). We smell different odours because each odour stimulates a unique pattern of receptors. The binding leads to a potential. Several receptor cells come together in the glomeruli in the Olfactory bulb. Mitral cells then send the signal form the olfactory bulb to the forebrain.
Working of the cilia
The mitral cells send the signal to the amygdala and the pyriform cortex. These pathways do not go though the thalamus. The pathway that does go through the thalamus is the one that goes to the
orbitofrontal cortex
(OFC) (Prefrontal cortex located behind the eye sockets (the orbits) that receives projections from the dorsomedial nucleus of the thalamus; plays a central role in a variety of emotional and social behaviors as well as in eating; also called orbital frontal cortex.)
The size of the receptor area determines how sensitive you are to odours. Human: 2-4 cm2, dog: 18 cm2, cat: 21 cm2
pheromones
: Odorant biochemical released by one animal that acts as a chemosignal and can affect the physiology or behavior of another animal.
Detected by a special olfactory system:
vomeronasal organ
(small group of sensory receptors connected by a duct to
the nasal passage). The receptors of this organ send their axons to the
accessory olfactory bulb
. This connects primarily with the amygdala and hypothalamus. This system plays a role in reproductive and social behavior.
Human olfactory processing
The brain analyzes common odors and human odours differently
Common odors: primary olfactory regions
Human odors: primary olfactory regions and posterior cingulate cortex, occipital cortex, and anterior cingulate cortex (also activated by visually emotional stimuli)
Processing a strangers odor, happens in the amygdala and insular cortex. These regions also become active in fearful situations
[H15]
