Learning & Memory

Memory Involves a number of regions in brain Amnesia (memory loss) studies reveal separate short- & long-term memory systems 8-35

Memory continued Hippocampus is critical for acquiring new memories & consolidating short- into long-term memory Amygdala is crucial for fear memories Prefrontal cortex 8-36

Memory continued Storage of memory is in cerebral hemispheres Higher order processing & planning occur in prefrontal cortex Prefrontal cortex

Memory Short-term: Memory of recent events. Medial temporal lobe: consolidates short term into long term memory. Hippocampus is critical component of memory. Acquisition of new information, facts and events requires both the medial temporal lobe and hippocampus.

Memory Long-term: Cerebral cortex stores factual information. Requires activation of genes, leading to protein synthesis. Growth of dendritic spines. Formation of new synaptic connections. Cerebral cortex stores factual information. Prefrontal lobes involve retrieval of parts of memories from different areas of the brain to use as a whole.

Long-Term Potentiation (LTP) Is increased excitability of a synapse after high frequency stimulation Glutamate activates AMPA & NMDA postsynaptic receptors in hippocampus 8-37

Long-Term Potentiation (LTP) continued Glycine or serine must coactivate NMDA receptors, opening Ca2+ channels Presynaptic Ca2+ levels also increase during LTP causing increased NT release Caused by NO released by postsynaptic cell which diffuses to presynaptic High postsynaptic Ca2+ causes LTP & growth of dendritic spines LTP is thought to be a form of synaptic learning 8-38

Neurogenesis in Hippocampus Appears to be crucial for learning & memory Hippocampus contains neural stem cells that continually produce new neurons (neurogenesis) Stress or depression impede learning & cause hippocampus to shrink Stress reduction & antidepressants return size to normal 8-39

Brain Structures & their Functions 8-40

Thalamus Comprises the majority of the diencephalon. Forms most of the walls of the 3rd ventricle. Acts as relay center for all sensory information (except olfactory) to the cerebrum

Thalamus continued Plays role in level of arousal Epithalamus contains choroid plexus which secretes CSF Also contains pineal gland which secretes melatonin Involved in sleep cycle & seasonal reproduction

Hypothalamus Is most important structure for homeostasis Contains neural centers for hunger, thirst, body temperature Regulates sleep, emotions, sexual arousal, anger, fear, pain, & pleasure Controls hormone release from anterior pituitary Produces ADH & oxytocin Coordinates sympathetic & parasympathetic actions 8-42

Pituitary Gland Is divided into anterior & posterior lobes Posterior pituitary stores & releases ADH (vasopressin) & oxytocin Both made in hypothalamus & transported to pituitary Hypothalamus produces releasing & inhibiting hormones that control anterior pituitary hormones 8-43

Circadian Rhythms Are body's daily rhythms Regulated by hypothalamus The master clock Adjusted daily by light from eyes Controls pineal gland secretion of melatonin which regulates circadian rhythms 8-44

Midbrain Contains: Superior colliculi -- involved in visual reflexes Inferior colliculi -- relays for auditory info 8-45

Midbrain Contains: Functions: Corpra quadrigemina Cerebral peduncles Substantia nigra Red nucleus Functions: Visual reflexes. Relay center for auditory information. Motor coordination. Red nucleus & substantia nigra -- involved in motor coordination S. nigra dopamine neurons degenerate in Parkinson’s Mesolimbic dopamine neurons are involved in reward & addiction

Hindbrain Contains pons, cerebellum & medulla cerebellum pons medulla 8-47

Hindbrain - Pons Contains several nuclei of cranial nerves & 2 important respiratory control centers Apneustic & pneumotaxic centers 8-48

Hindbrain - Cerebellum 2nd largest structure in brain Receives input from proprioceptors (joint, tendon, & muscle receptors) Involved in coordinating movements & motor learning cerebellum 8-49

Hindbrain - Medulla Contains all tracts that pass between brain & spinal cord & many nuclei of cranial nerves & several crucial centers for breathing & cardiovascular systems 8-50

Reticular Formation Is complex network of nuclei & fibers spanning medulla, pons, midbrain, thalamus, & hypothalamus Functions as reticular activating system Sets level of arousal of cerebral cortex to incoming sensory information 8-51

Spinal Cord 8-52

Spinal Cord Tracts Sensory info from body travels to brain in ascending spinal tracts Motor activity from brain travels to body in descending tracts 8-53

Ascending Spinal Tracts Ascending sensory tracts decussate (cross) so that brain hemispheres receive info from opposite side of body Same for most motor tracts from brain 8-54

Peripheral Nervous System 8-57

Peripheral Nervous System (PNS) Consists of nerves that exit from CNS & spinal cord, & their ganglia (= collection of cell bodies outside CNS) 8-58

Cranial Nerves Consist of 12 pairs of nerves 2 pairs arise from neurons in forebrain 10 pairs arise from midbrain & hindbrain neurons Most are mixed nerves containing both sensory & motor fibers 8-59

Spinal Nerves Are mixed nerves that separate next to spinal cord into dorsal & ventral roots Dorsal root composed of sensory fibers Ventral root composed of motor fibers 8-60

Reflex Arc Stimulation of sensory receptors evokes AP that are conducted into spinal cord. Synapses with motor neuron. Conducts impulses to muscle and stimulates a reflex contraction. Brain is not directly involved.

Memory Involves a number of regions in brain Amnesia (memory loss) studies reveal separate short- & long-term memory systems 8-35

Memory continued Hippocampus is critical for acquiring new memories & consolidating short- into long-term memory Amygdala is crucial for fear memories Prefrontal cortex 8-36

Memory continued Storage of memory is in cerebral hemispheres Higher order processing & planning occur in prefrontal cortex Prefrontal cortex

Memory Short-term: Memory of recent events. Medial temporal lobe: consolidates short term into long term memory. Hippocampus is critical component of memory. Acquisition of new information, facts and events requires both the medial temporal lobe and hippocampus.

Memory Long-term: Cerebral cortex stores factual information. Requires activation of genes, leading to protein synthesis. Growth of dendritic spines. Formation of new synaptic connections. Cerebral cortex stores factual information. Prefrontal lobes involve retrieval of parts of memories from different areas of the brain to use as a whole.

Long-Term Potentiation (LTP) Is increased excitability of a synapse after high frequency stimulation Glutamate activates AMPA & NMDA postsynaptic receptors in hippocampus 8-37

Long-Term Potentiation (LTP) continued Glycine or serine must coactivate NMDA receptors, opening Ca2+ channels Presynaptic Ca2+ levels also increase during LTP causing increased NT release Caused by NO released by postsynaptic cell which diffuses to presynaptic High postsynaptic Ca2+ causes LTP & growth of dendritic spines LTP is thought to be a form of synaptic learning 8-38

Neurogenesis in Hippocampus Appears to be crucial for learning & memory Hippocampus contains neural stem cells that continually produce new neurons (neurogenesis) Stress or depression impede learning & cause hippocampus to shrink Stress reduction & antidepressants return size to normal 8-39

Brain Structures & their Functions 8-40

Thalamus Comprises the majority of the diencephalon. Forms most of the walls of the 3rd ventricle. Acts as relay center for all sensory information (except olfactory) to the cerebrum

Thalamus continued Plays role in level of arousal Epithalamus contains choroid plexus which secretes CSF Also contains pineal gland which secretes melatonin Involved in sleep cycle & seasonal reproduction

Hypothalamus Is most important structure for homeostasis Contains neural centers for hunger, thirst, body temperature Regulates sleep, emotions, sexual arousal, anger, fear, pain, & pleasure Controls hormone release from anterior pituitary Produces ADH & oxytocin Coordinates sympathetic & parasympathetic actions 8-42

Pituitary Gland Is divided into anterior & posterior lobes Posterior pituitary stores & releases ADH (vasopressin) & oxytocin Both made in hypothalamus & transported to pituitary Hypothalamus produces releasing & inhibiting hormones that control anterior pituitary hormones 8-43

Circadian Rhythms Are body's daily rhythms Regulated by hypothalamus The master clock Adjusted daily by light from eyes Controls pineal gland secretion of melatonin which regulates circadian rhythms 8-44

Midbrain Contains: Superior colliculi -- involved in visual reflexes Inferior colliculi -- relays for auditory info 8-45

Midbrain Contains: Functions: Corpra quadrigemina Cerebral peduncles Substantia nigra Red nucleus Functions: Visual reflexes. Relay center for auditory information. Motor coordination. Red nucleus & substantia nigra -- involved in motor coordination S. nigra dopamine neurons degenerate in Parkinson’s Mesolimbic dopamine neurons are involved in reward & addiction

Hindbrain Contains pons, cerebellum & medulla cerebellum pons medulla 8-47

Hindbrain - Pons Contains several nuclei of cranial nerves & 2 important respiratory control centers Apneustic & pneumotaxic centers 8-48

Hindbrain - Cerebellum 2nd largest structure in brain Receives input from proprioceptors (joint, tendon, & muscle receptors) Involved in coordinating movements & motor learning cerebellum 8-49

Hindbrain - Medulla Contains all tracts that pass between brain & spinal cord & many nuclei of cranial nerves & several crucial centers for breathing & cardiovascular systems 8-50

Reticular Formation Is complex network of nuclei & fibers spanning medulla, pons, midbrain, thalamus, & hypothalamus Functions as reticular activating system Sets level of arousal of cerebral cortex to incoming sensory information 8-51

Spinal Cord 8-52

Spinal Cord Tracts Sensory info from body travels to brain in ascending spinal tracts Motor activity from brain travels to body in descending tracts 8-53

Ascending Spinal Tracts Ascending sensory tracts decussate (cross) so that brain hemispheres receive info from opposite side of body Same for most motor tracts from brain 8-54

Peripheral Nervous System 8-57

Peripheral Nervous System (PNS) Consists of nerves that exit from CNS & spinal cord, & their ganglia (= collection of cell bodies outside CNS) 8-58

Cranial Nerves Consist of 12 pairs of nerves 2 pairs arise from neurons in forebrain 10 pairs arise from midbrain & hindbrain neurons Most are mixed nerves containing both sensory & motor fibers 8-59

Spinal Nerves Are mixed nerves that separate next to spinal cord into dorsal & ventral roots Dorsal root composed of sensory fibers Ventral root composed of motor fibers 8-60

Reflex Arc Stimulation of sensory receptors evokes AP that are conducted into spinal cord. Synapses with motor neuron. Conducts impulses to muscle and stimulates a reflex contraction. Brain is not directly involved.