NEURExam 3

Homeostasis

Maintaining a regular temperature in the body

Alleostasis

The brain is predicting that something will happen and avoids error rather than correcting errors, depends on the hypothalamus

Sex hormones

Male and female start with the same anatomy during early prenatal stage

The SRY gene produces androgens (testosterone)

Females produce more estrogens

Organizing effects (permanent)

In the first trimester, sex hormones (mainly testosterone) determines whether the body develops male or female

Organizing effects: Childhood behavior

Prenatal hormones alter the brain that influence differences between boys and girls activities and interests

Genetic and prenatal influences on sexual orientation

Sexual orientation may depend on testosterone levels during a first trimester

Stress can decrease testosterone

A gene on the X chromosome received from the mother could be linked to sexual orientation

Activating effects (temporary)

Oxytocin important for reproductive behavior, contractions, breast feeding, orgasm

Hemianopia/hemianopsia

Blindness of half-visual field b/c of damage in left or right V1 (primary visual cortex)

Cortical blindness

Total/partial loss of vision

Blindsight

Individuals have loss of vision but can unconsciously detect/react to visual stimuli

Cortical color blindness

Loss of color vision due to V4 damage, imagery and memory affected too

Visual agnosia

Inability to recognize visual information, geniculostriate , and ventral pathways

Prosopagnosia

Difficulty recognizing familiar faces, bilateral damage of fusiform areaa

Alexia/word blindness

Inability to read, damage of left fusiform area affect words recognition, they can trace words to readO

Object agnosias

Apperceptive: Inability to develop a percept (can’t copy an object)

Associative agnosia: Inability to recognize an object despise its apparent perception (can copy an object, not recognize)

Ataxia

Simultagnosia - Patients have problems to perceive more than one object at a time, due to damage in different areas (dorsal stream), can occur in patients with Balint’s syndrome - spatial attention problem

Auditory receptors

Auditory pathways

Axons leave the cochlea (auditory nerve to the medulla)

Next synapse occurs in the inferior colliculus (midbrain)

Next synapse occurs in the medial geniculate nucleus of the thalamus

Last stop is the auditory cortex (A1)

Tonotopic map

Primary auditory cortex (A1): Cells in the primary auditory cortex have a preferred tone

Neurons located to the left respond more to low frequencies vice versa

Auditory what pathway

Starts in A1, ends in anterior temporal sulcus

Auditory where pathway

Starts in A1, ends in posterior temporal cortec and parietal cortex

Temporal lobe: Superior temporal gyrus

Auditory ventral stream

Temporal lobe: Inferior temporal gyrus

Visual ventral stream

Temporal lobe: Middle temporal gyrus

Auditory and visual processes

Temporal lobe: Medial temporal region

Amygdala and hippocampus

Superior temporal sulcus

Active when looking at motion, cross modal matching

Medial temporal lobe: Insula

Connects brain and body, awareness of body, reacts the most when emotions are high

Medial temporal lobe: parahippocampal gyrus

Memory encoding, spatial navigation

Medial temporal lobe: Fusiform gyrus

Visual processing

Medial temporal lobe: Amygdala

Affective responses to sensory input, associated with fear response

Medial temporal lobe: Hippocampus

Spatial navigation, conscious memory

Ventral pathway in temporal lobe

Object recognition/developing object categories

Superior temporal sulcus function

Biological motion perception and social cognition (people’s intentions)

Amusia (Heschl’s gyrus)

Impairment to make pitch discriminations

Auditory hallucinations

Spontaneous activity in the auditory regions (perceiving noise with no noise)

Wernicke’s aphasia

Disturbed word recognition

Anterograde amnesia

Bilateral removal of the medial temporal lobe

Temporal-lobe personality (Geschwind syndrome)

Pedantic speech, paranoia, aggressive outbursts, damage of temporal lobe

Posterior parietal cortex function

Spatial information

Somatosensory (anterior parietal) cortex function

Sensory information from the body

Phantom limb experience

Homunculus (body maps), the area of the brain previously responsible for the limb receives no input, requiring neighboring brain regions to take over that area

Anosognosia

Unawareness of illness

Balint’s syndrome

Simultagnosia and optic ataxia, has issues reaching object and can only pay attention to one object at a time (posterior parietal lobe)

Neglect Syndrome

Damage to the right hemisphere causes patients to fail to attend/perceive the left side of space or their own body

The Gerstmann syndrome

Dysgraphia (problems with writing), dyscalculia (problems with numbers), problems with right-left discrimination

Apraxia

Loss of skill movement not caused by weakness (clumsiness)

Problems with sensoriomotor transformation (posterior parietal region)

You know what’s going to happen so it’s not unexpected (efference copy-corollary discharge)

Corollary discharge

The brain’s memo (efference copy) sent to sensory systems, predicting the sensory feedback a movement will cause

Somatosensory cortex

Post central gyrus

Posterior parietal cortex

Superior parietal lobule, inferior parietal lobule

Somatic nervous system

System where the brain controls movement and receives sensory information from the body (spinal nerves) and head and neck (cranial nerves)

Body

Spinal nerves

Head and neck

Cranial nerves

Autonomic nervous system

Neurons that receive information from and send commands to the heart, intestines

Sympathetic nervous system

Increases breathing/heart rate, decreases digestive activity, linked to the spinal cord, most sympathetic axons release norepinephrine

Parasympathetic nervous system

Decreases heart rate, increases digestive activity, releases acetylcholine into the organs and serotonin

Vagus nerve

Primary component of PNS

Primary motor cortex (M1)

Stimulation elicits movements

Prefrontal cortex

Movement organization and motor inhibition of automatic movements

Mirror neurons

In the premotor cortex, they are both active when we observe someone doing something and we do that same thing, important for learning, intentions empathy

Subcortical areas: Basal ganglia

Muscle memory, learning new habits, automatic responses

Basal ganglia pathways

Direct: BS → Thalamus (initiates movement)

Indirect: Terminates movement and inhibits unwanted movements

Subcortical areas: Cerebellum

Coordination

Ataxia: Resembles alcohol intoxication

Primary motor cortex

M1

Major subdivisions of the frontal lobe

Premotor cortex - yellow, motor cortex - green, prefrontal cortex - blue

Anterior cingulate cortex ACC

PFC, contains spindle neurons, related to socialization/empathy

Dorsal ACC

Towards the back, relations to movement, attention, cognitive control, consciousness

Ventral ACC

Towards the belly, connections with default mode network, memory areas, important for self-referential thinking, emotion

PFC: Dorsolateral prefrontal cortex

Attention

PFC: Orbitofrontal cortex

Modulate physiological responses of the body

PFC: Ventromedial

Emotion regulation, decision making, controlling fear

Ventrolateral PFC

Cognitive control, inhibitory motor control, emotional regulation

Frontal lobe lesions

Disturbance of motor functions

Can’t make fine movements (primary motor cortex)

Problems with movement programming (premotor)

Problems with voluntary gaze (FEF)

Problems with corollary discharge

Broca’s aphasia (non-fluent speech, frontal lobe)

Lesions of prefrontal lobe

Problems with

Loss of behavioral spontaneity, solving problems

Rule breaking and risk taking (ACC)

Perseveration and response inhibition + associative learning + temporal memory + reduced interest in sexual behavior (DLPFC)

Abnormal sexual behavior + pseudodepression + pseudopsychopathy + rule breaking/risk taking (OFC)

The stroop test

Colored words, asses inhibitory control

Wisconsin sorting cards

Evaluate frontal lobe dysfunction

DLPFC

Reduced interest in sexual behavior, Problems with temporal memory, Perseveration and response inhibition, Problems learning from experience

OFC

Pseudodepression, Pseudopsychopathy, Abnormal sexual behavior, Rule breaking and risk taking

ACC: Lesions

Rule breaking and risk taking

Premotor cortex

Selects movements, include’s Broca’s area, supplementary motor cortex, dorsal + ventral premotor cortex, contains mirror neurons, receives connections from parietal + other frontal areas