Instrumental Learning

Instrumental learning   Learning to benefit from experience. Several processes are involved: o Reinforcement: “stamping in” behaviours that result in positive consequences. o Punishment: “stamping out” behaviours that result in negative consequences. o Extinction: relinquishing behaviours that have neutral consequences. o Motor learning: acquisition of new behaviours when necessary. o Strengthening or weakening of the connection between perception of the discriminative stimuli and the motor apparatus that produces the response.  The role of the basal ganglia in acquisition of new behaviours (motor learning): o Role in motor disorders: Parksinson’s disease, athetosis and choreiform movements, Huntington’s disease. o Circuits responsible for instrumental conditioning – must connect sensory association cortices (where perception takes place) to motor association cortices (where movements are planned and executed). There are two such pathways: o Direct transcortical connections – acquisition of complex behaviours that involve deliberation or instruction. o Connections via the basal ganglia and thalamus. Changing from conscious to unconscious behaviour: o At first, learning requires a great deal of the brain’s resources as a large amount of concentration is needed. o As behaviours are learned and perfected, they become increasingly automatic and require less conscious deliberation. o This corresponds with the behaviours being taken over by the basal ganglia. There is no longer a need to think about the behaviour; transcortical circuits can be devoted to other tasks. Automatisation of behaviour seems to be disrupted by blocking NMDA receptors in the basal ganglia, suggesting that LTP is involved. Neural circuits involved in reinforcement: o 1954, James Olds and Peter Milner: rats will bar press for electrical stimulation of certain parts of the brain. o Highest rates of responding were supported by electrodes implanted in the medial forebrain bundle (MFB), which connects the ventral tegmental area (VTA) to the nucleus accumbens. o This is the mesolimbic dopamine system – the nucleus accumbens has high density of dopamine receptors. o Perhaps the primary reinforcement system in the brain. o Anything that activates this pathway will produce a reinforcing effect. o Stimulation of VTA, or the MFB, or the administration of cocaine or amphetamine, as well as the occurrence of natural reinforcers, cause the release of dopamine in the nucleus accumbens. o fMRI scans show that reinforcing events actvivate the nucleus accumbens in humans.      o This pathway aso appears to play a role in addiction to most (but not all) drugs. Functions of the reinforcement system: o Detect the presence of a reinforcing stimulus. o Strengthen the connections between the neurons that detect the discriminative stimulus and the neurons that produce the instrumental response. o There appear to be three important inputs to the VTA that are involved in reinforcement from the amygdala, the lateral hypothalamus and the prefrontal cortex. o The medial forebrain bundle. Relational learning     Two types of amnesia: o Retrograde amnesia: forgetting the past (events before the brain damage occurred). o Anterograde amnesia: inability to form new memories for events after the brain damage occurred. Korsakoff’s syndrome (usually due to chronic alcoholism) is characterised by severe anterograde amnesia. Anterograde amnesia can also result from damage to the temporal lobes. Patient H.M. o Damage to the medial temporal lobe. o Had intact working memory and procedural memory, but impaired declarative memory. Measuring memory  Stroop test.  Wechsler memory scale (long term memory).