Types of Impairments

Attention

Smoking associated with loss of brain volume

Cortical activity of never-smokers was larger, reflecting greater processing attention

Memory

MDMA produces neurotoxic damage in both animals (Wang et al. 2004) and humans (Cowan et al.)

(Brown et al. 2010) - investigated memory deficits in human ecstasy users

Verb Paired Associates (VPA) - i.e frog-table
Stem Cued Recall Task - finish a word from a list of previously seen

Ecstasy users showed selective memory impairment in the VPA task but not in cued stem completion

Reversal Learning

Probes the ability to change behaviour in the face of changed outcomes that occur as a result of that behaviour

Acquisition: Reinforcement learning to do the 'right' thing
Reversal Stage: The options are switched

The number of errors before switching to the new stage indexes the inability to learn the new response strategy

Cocaine and methamphetamines render subjects less able to learn to switch strategies

Habits / Response Inhibition

Two types of instrumental behaviour

Goal-directed instrumental response - idea of the reward + response that should produce that reward
Habitual instrumental response - occurs after training | context elicit the response

There needs to be a balance between these two types of response.

Even after the devaluation procedure, amphetamine-injected rats still decided to press the lever. This indicates that they were less able to act in a goal-direct instrumental response.