Brain: Higher Functions Learning, Consciousness and Behavior

Divisions of the Nervous System

Electroencephalography (EEG) The electroencephalograph (EEG) is the printout of an electronic device that uses scalp electrodes to monitor the internal neural activity in the brain cortex.

EEG as Clinical Tool EEGs provide diagnostic information about the location of abnormal activity in the brain, such as shown in this record typical of a patient undergoing an epileptic seizure. EEGs record largely the surface electrical activity of underlying brain areas Activity largely due to summated graded potentials of many neurons Amplitude shows how much activity (degree of summation and/or number of neurons)

EEG waves Alpha wave –dominant wave of a conscious relaxed adult with their eyes closed; associated with parietal-occipital lobes and decreased attention level 8-13Hz, amp= 50mcV Decreased freq. by low blood glucose, low body temp., low gluco-corticoids or high PCO2 Beta wave –dominant wave of attentive adult; associated primarily with frontal lobe activity Arousal response >13Hz, lower amp

EEG waves during sleep Theta waves –slower frequency (4-8 Hz) but higher amplitude; assoc. with hippocampus and seen in children occipital lobes Delta waves –large, slow (<4/sec) pattern of deep NREM sleep

Sleep Patterns NREM Stage 1 4: decreasing eye and skeletal muscle movement, increased threshold for arousal, increase size but decrease freq. of EEG REM: EEG freq. increases with less amplitude (alpha like), increase HR, Resp. Rate, and eye movement, but still in deep sleep, high oxygen consumption in brain; dream sleep 4-5 cycles of NREM/REM sleep each night (every ~90 min) (Persistent Insomnia can be fatal)

RAS (Reticular Activating System) Brainstem nuclei intermingled with bundles of axons Receives and integrates input from all regions of CNS Involved in motor function, CV and respiratory control, attention, sleep/wakefulness Most of the biogenic amine NT are released from axons of RAS Aminergic neurons may dominate wakefulness and cholinergic neurons may dominate sleep Preoptic area has GABAnergic neurons that inhibit RAS and hypothalamus Suprachiasmatic nucleus regulates the pineal; which regulates sleep’s timing

Importance of Sleep Slow wave sleep is thought to be restorative to brain function (Children have more total sleep time and are in stage 4 more than adults); Elderly have about the same total sleep time as adults but broken into smaller episodes, also spend less time in REM. Time spent in Stage 4 declines with age. Person consistently deprived of REM may become moody or depressed; may exhibit other personality disorders

Coma & Brain Death Coma is a severe loss in mental function due to brain damage; sustained loss of arousal (even with heavy stimuli), behavior response is lost, no sleep/wake cycles Persistent Vegetative State (irreversible coma) –sleep/wake cycles are present; no sign of external awareness

Learning & Memory Learning –acquisition and utilization of information from past experience Memory –relatively permanent storage of information Declarative memory –retention of conscious experience, facts, etc.; uses Limbic system & cortex (amygdala, hippocampus & thalamus) Procedural memory –knowledge of how to do something (skilled behaviors); uses sensory cortex, basal nuclei, & cerebellum

Possible Memory Circuits Procedural Declarative Sensory Inputs Sensory & Motor Inputs Association Areas Association Areas Medial Temporal Lobe (hippocampus, amygdala) Substantia Nigra DA Basal Nuclei ACh Basal Forebrain Thalamus Thalamus Prefrontal cortex ACh Premotor cortex

Memory Processing Automatic long term memory linked to noxious stimuli. Many long term memories may be unretrievable consciously, but may still exist within the brain ??

Patient with right parietal lobe damage.

Dependency