Transcript The Brain
SURVEY OF MODERN PSYCHOLOGY The Brain We will discuss: The parts of the brain and what they do Neurotransmitters The effects of various drugs on the brain and neurotransmitters Some general notes about the brain Bilaterally symmetrical along the longitudinal fissure The left and right side communicate via the corpus callosum Contra lateral control – the left side of the brain controls the right side of the body and vice versa The parts of the brain Going from the back of the brain towards the front, functions are more advanced Hindbrain Midbrain Forebrain Hindbrain Hindbrain Cerebellum Balance Damage (permanent or chemical) causes a wide staggering gait Performance and timing of skilled movements Damage here causes tremors during movement and an inability to perform rapidly alternating movements Ex. This would interfere with a skill such as typing Pons Regulating the brain’s level of attentiveness Initiating sleep and dreaming Integrates movements of and sensations from the facial muscles, eyes, tongue, and ears Medulla Controls basic biological functions Cardiovascular and respiratory systems Reflexes (e.g. coughing, swallowing, sneezing) Maintains balance by controlling head orientation and limb positions with respect to gravity) Midbrain (Mesencephalon) Midbrain (Mesencephalon) •Includes the Tectum and Tegmentum •Tracking moving stimuli (visual and auditory) •Controls eye movements •Coordinates simple movements (controlled by the hindbrain) to form more complicated wholes •Damage here makes the organism unable to perform purposeful behaviors •E.g., an animal can move and chew, but will not initiate a search for food when it is starving Forebrain Forebrain Parts: Cerebral cortex Limbic system Thalamus Hypothalamus Forebrain Thalamus Receives sensory information and conveys it to the relevant structures Hypothalamus Controls the autonomic nervous system, endocrine system, and major biological drives Basal ganglia Control of movement Damage/degeneration here causes Parkinson’s disease E.g., vision and other senses, balancing information for movement Weakness, tremors, rigidity of limbs, poor balance, difficulty in initiating movements Includes the hippocampus and amygdala Learning Memory Storing new information into long term memory Some regions are involved in emotions – feeling and expressing emotion, emotional memories, and recognition of signs of other people’s emotions Stimulation generally produces feelings of anxiety and/or rage Cerebral Cortex Frontal lobe Parietal lobe Temporal lobe Occipital lobe Cerebral Cortex Frontal lobe Parietal lobe Senses (touch, pain, temperature) Temporal lobe Memory, strategy formation, response inhibition Conscious thought Hearing Occipital lobe Vision The frontal lobe is largely linked to personality Much of what we know comes from instances of brain damage or injury Phineas Gage In an accident in the mid 1800s, a large steel rod went through his head He survived, but friends said that there were major changes in his personality and was “no longer Gage” In general, injury to the frontal lobe results in: Lack of spontaneity Few facial expressions and gestures Limited and non-fluent speech Strategy formation Lack of response inhibition The person does not understand rules and therefore has difficulty following rules •The Hemispheres •There is a lot of popular theory/cultural belief that the left and right hemispheres serve vastly different functions. •In reality, both hemispheres do play some part in almost all areas. •Most likely, one side is simply more effective and efficient in performing specific tasks. •The division of labor is described as seen in right handed people. Visual System Left Hemisphere Letters Words Right Hemisphere Complex geometric patterns Faces Auditory System Left Hemisphere Language related sounds Right Hemisphere • Non-language, environmental sounds • Music Somatosensory System Left Hemisphere Unknown Right Hemisphere • Tactile recognition of complex patterns • E.g., Braille Movement Left Hemisphere Complex voluntary movement Right Hemisphere • Movements in spatial patterns Memory Left Hemisphere Verbal memory Right Hemisphere • Nonverbal memory Language Left Hemisphere Speech Reading Writing Arithmetic Right Hemisphere • Prosody • Narrative • Inference Spatial Processes Left Hemisphere Unknown Right Hemisphere • Geometry • Sense of direction • Mental rotation of shapes Final Notes on Hemispheres The left and right hemispheres are joined by the corpus callosum. In some severe cases of epilepsy, surgery is performed to cut the corpus callosum. 1981: the Nobel Prize was given to Roger Sperry for his research on “split brains” A participant was prevented from seeing the object and given a pencil in their left hand The nerve impulse therefore reached the right hemisphere, but not the left The participant could generally demonstrate what the pencil should be used for with motions, but could not name the object They could only name the object if it was placed in the right hand. When shown a stimulus is shown on the right side (processed by the left hemisphere) such as words, it is processed faster than if the same was shown on the left side. The right hemisphere needs to send the image to the left side for processing. Brain Damage Apraxia Disturbances in movement Lesions in the frontal lobe; disconnect in primary and nonprimary motor areas Disturbances in initiation or organization of voluntary actions Ex. Unable to wave Ex. When trying to bake, a person might try to repeatedly break the same egg, or put a measuring spoon in a bowl as well as the ingredient Brain Damage Agnosia Inability to identify familiar objects using a particular sense Visual agnosia – able to identify a car key by touch, but not by appearance Able to recognize parts but not a whole Prosopognosia – inability to identify faces This might be the inability to recognize a face as a face Brain Damage Aphasia Disturbances in language Caused by damage by lesions, usually in the left hemisphere Nonfluent aphasia Inability to produce speech, but comprehending what is said Fluent aphasia Inability to comprehend what is said Speech is made of filler words, with no information People who can hear sometimes learn Sign Language to communicate HOWEVER Deaf people who suffer the same brain damage experience the same difficulties in communication as hearing people with aphasia Neurons Parts of a neuron: Dendrites Receive impulses from other neurons Cell body Axon Synapse (the space between cells) Communication occurs across synapses via neurotransmitters Neurotransmitters are usually ejected, brought back into axons, and then reused Lock and key model: the transmitter will only have an effect if it fits into the receptor molecules Neurotransmitters The ones we will discuss are: Dopamine Serotonin Norepinephrine Acetylcholine GABA Glutamate Endorphins Dopamine Normal function Produces sensations of pleasure and reward Used by the central nervous system (CNS) neurons involved in voluntary movement Problems associated with imbalance Schizophrenia Parkinson’s disease Substances that affect the action of this neurotransmitter Cocaine Amphetamine Alcohol Serotonin Normal function Regulates sleep and dreaming, mood, pain, aggression, appetite, and sexual behavior Problems associated with imbalance Depression Some anxiety disorders Obsessive compulsive disorder Substances that affect the action of this neurotransmitter Hallucinogenics Norepinephrine Normal function Used by neurons in the automatic nervous system and by neurons in almost every region of the brain Controls heart rate, sleep, stress, sexual responsiveness, vigilance, and appetite Problems associated with imbalance High blood pressure Depression Substances that affect the action of this neurotransmitter Tricyclic antidepressants Beta blockers Acetylcholine Normal function The primary neurotransmitter used by neurons carrying messages form the CNS Involved in some kinds of learning and memory Problems associated with imbalance Some muscular disorders Alzheimer’s disease Substances that affect the action of this neurotransmitter Nicotine Black widow spider venom Botulism toxin GABA Normal function The most prevalent inhibitory neurotransmitter in neurons of the CNS Problems associated with imbalance Anxiety Epilepsy Substances that affect the action of this neurotransmitter Barbiturates “Minor” tranquilizers (ex. valium) Alcohol Glutamate Normal function The primary excitatory neurotransmitter in the CNS Involved in learning and memory Problems associated with imbalance Release of excessive glutamate causes brain damage after strokes Substances that affect the action of this neurotransmitter PCP (angel dust) Endorphins Normal function Pleasurable sensations Control of pain Problems associated with imbalance Lowered levels resulting from opiate addiction Substances that affect the action of this neurotransmitter Opiates (opium, heroin, morphine, methadone) Drugs Drugs act on synapses (the spaces between neurons) and affect the response to neurotransmitters Agonists facilitate effects Antagonists inhibit effects Dependence and addiction are characterized by tolerance and withdrawal Drugs Physical vs. psychological dependence Physical addiction is often defined by the physiological effects that happen when a person stops using a drug Psychological dependence involves the emotional feeling of wanting the drug either to produce pleasure or avoid discomfort Psychological addiction tends to be more difficult to overcome than physical addiction Positive reinforcement – if it feels good, keep doing it! Withdrawal is the opposite of whatever the effects of the drug are (E.g., withdrawal from an opiate causes agitation) Types of Drugs and their Effects Opiates Stimulants Nicotine Alcohol and Barbiturates Cannabis/THC Opiates Naturally occurring opiates in the brain block pain Cause analgesia, hypothermia, sedation, reinforcement Act on GABA and dopamine Opiate blockers may be used to treat addiction (no effect, therefore no reinforcement) Stimulants Dopamine agonists Stimulate the release of dopamine and inhibit the reuptake Euphoric, active, and talkative Hallucinations, paranoia, mood disturbances, repetitive behavior Similar to schizophrenia Nicotine Dopamine and acetylcholine agonists Often harder to quit than “hard” drugs Withdrawal includes anxiety, restlessness, insomnia, inability to concentrate Nicotine antagonists can also reduce cocaine cravings Alcohol and Barbiturates Dopamine and GABA agonists Small doses produce mild euphoria and inhibits anxiety – stops the punishing effects of aversive stimuli Alcohol: Withdrawal can be fatal Ex. if an animal is given shocks when it performs a particular action, it will stop. If given alcohol, it will not learn and keeps performing the response Convulsions and seizures Chronic alcoholism can lead to Korsakoff’s Syndrome This is caused by a vitamin deficiency – frequent alcohol use can block the absorption of some vitamins Permanent anterograde amnesia (inability to form new memories, but still having old ones) Confabulation – making up memories Can have elements of reality or be completely imaginary Cannabis/THC Cannabis: Dopamine agonist Particularly affects the hippocampus, causing memory problems Long term use can cause inattentiveness, impaired memory, reduced ability to multitask