Consciousness and Behavior

Defined either by (1) behavior – ranging from attentive and alert to coma and (2) electrical pattern of brain activity, recorded as an electroencephalogram (EEG).

Electroencephalogram

The electric potential difference between two points on the scalp. The amplitude indicates a degree of synchronous activity and frequency indicates responsiveness (low frequency = sleep to high frequency = alert).

Wakeful State

The high frequency, low amplitude wave pattern of an awake relaxed adult is called the alpha rhythm. As people become more attentive, the wave pattern becomes low amplitude, high-frequency oscillations called the beta rhythm. This transformation is called EEG arousal.

Sleep

Neural Substrates of States of Consciousness

Periods of sleep and wakefulness show a circadian or daily rhythm, the clock timing of which depends on the suprachiasmatic nucleus. Aminergic neurons that release norepinephrine or serotonin are dominant during wakefulness while cholinergic neurons are dominant during REM sleep. NREM sleep is intermediate to these two states.

Coma and Brain Death

Coma is a severe decrease in mental function due to structural, physiological or metabolic impairment of the brain. A person in a coma is characterized by a sustained loss of capacity for arousal even in response to vigorous stimulation. There is no outward behavioral expression of any mental function and sleep-wake cycles disappear. Brain death is an irreversible coma without drug intoxication. There should not be any functioning neural tissue above the spinal cord.

Conscious Experiences

Directed Attention

Avoidance of irrelevant stimuli and focusing on relevant stimuli is called directed attention. Preattentive processing of information directs attention toward meaningful stimuli before we focus on them. Focusing is possible without making any behavioral response. If it is followed by an orientation toward the stimulus source, it is called the orienting response. If the behavioral response to the stimulus progressively decreases as it is found to be irrelevant, it is called habituation.

Neural Mechanisms for Directed Attention

Motivation and Emotion

Motivation

Motivation is responsible for goal-directed behavior. Motivation leads to hormonal, autonomic or behavioral responses. Behavior related directly to homeostasis is called primary motivated behavior. If the relation between the behavior and the goal is indirect, it is secondary motivated behavior and this is influenced by factors called incentives such as habit, learning, etc. Motivations may be shaped by rewards (positive reinforcers) or punishments (negative reinforcers). The mesolimbic dopamine pathway is involved in the motivation process.

Emotion

An individual’s assessment of the environment and their disposition to it. Amygdala, a cluster of nuclei on the temporal lobe, is central to emotional states.

Altered States of Consciousness

Schizophrenia

Information is not properly regulated in the brain. Motor control is abnormal. Dopamine pathways are overactive.

Mood disorders: depressions and bipolar disorders

The mood is sustained inner emotion that affects the person’s perception of the world. Depressive disorders are indicated by loss of energy, interest, and anxiety. Bipolar disorders are swings between depression and mania -an abnormally elated mood. It can be treated by electroconvulsive therapy (ECT) in which pulses of electric current are used to activate a large number of neurons and alter neurotransmitter function to down-regulate some postsynaptic receptors.

Psychoactive substances, dependence, and tolerance

Psychoactive substances exert their actions by altering neurotransmitter-receptor interactions. Psychological dependence is craving for a substance and an inability to stop. Physical dependence requires one to take the substance to avoid withdrawal physiological symptoms occurring with the cessation of substance use. Tolerance to a substance occurs when increasing doses of a substance are required to achieve the desired effect. Cross-tolerance is the development of tolerance to one substance due to the use of another.

Learning and Memory

Learning is the acquisition and storage of information as a consequence of experience. Measured y an increase in the likelihood of a particular behavior in response to a stimulus. Rewards and punishment influence learning.

Memory

Permanent stored form of learned information. Processes that mediate between learning and memory are called memory encoding. Two types: (1) Declarative memory is knowledge of one’s past experience of the world. The limbic system is important for this type of memory. (2) Non-declarative memory is memory for the performance of skilled behaviors. The sensorimotor cortex, basal ganglia, and cerebellum are important for this type of memory.

Working memory

Working memory is the primary or short-term memory that registers and retains information for a very short time. It makes possible a temporary impression of one’s present environment in a readily accessible form. Focusing attention is important for memory-based skills.

Cerebral Dominance and Language

In the majority of the population, the left cerebral hemisphere is specialized to produce language. Distinct areas are specialized for different language skills. During development, assignment of language functions can take place in either hemisphere but it progressively shifts to the left. Although language skills emerge spontaneously in all children, they must be exposed to language during a critical period. Verbal memory is associated with the left hemisphere and nonverbal memory is associated with the right.