The impact of asymmetrical light input on cerebral hemispheric specialization and interhemispheric cooperation.

Hemispheric specialization potentially provides evolutionary advantages by enhancing cognitive capacities. However, separation of function might be advantageous only with the presence of commissural systems allowing for efficient information exchange and cooperation between the hemispheres. Here we investigate hemispheric cooperation in pigeons as they possess an asymmetrically organized visual system that develops in response to biased ontogenetic light stimulation. This allows comparison of the integration capacities of lateralized (light-incubated) and non-lateralized (dark-incubated) animals. We show that pigeons integrate information learnt separately with each hemisphere when confronted with a transitive reasoning task that they cannot solve with the knowledge of one hemisphere alone. Impairments in dark-incubated birds demonstrate that this ability depends on asymmetrical embryonic light stimulation. Our study provides for the first time direct evidence that lateralized environmental experience not only induces hemispheric specialization, but also affects the efficiency of interhemispheric crosstalk. Environmental factors can influence the tight interplay between the hemispheres, which in turn determines cognitive abilities.

Learning from positive and negative monetary feedback in patients with alcohol dependence.

BACKGROUND: Chronic and excessive consumption of alcohol is associated with structural, physiological, and functional changes in multiple regions of the human brain including the prefrontal cortex, the medial temporal lobe, and the structures of the reward system. The present study aimed to assess the ability of alcohol-dependent patients (ADP) to learn probabilistic stimulus-reward contingencies and to transfer the acquired knowledge to new contexts. During transfer, the relative preference to learn from positive or negative feedback was also assessed. METHODS: Twenty-four recently detoxified ADP and 20 healthy controls engaged in a feedback learning task with monetary rewards. The learning performance per se and transfer performance including positive versus negative learning were examined, as well as the relationship between different learning variables and variables comprising alcohol and nicotine consumption patterns, depression, and personality traits (harm avoidance and impulsivity). RESULTS: Patients did not show a significant general learning deficit in the acquisition of stimulus-response-outcome associations. Fifteen healthy subjects and 13 patients reached the transfer phase, in which ADP showed generally lower performance than healthy controls. There was no specific deficit with regard to learning from positive or negative feedback. The only near-significant (negative) correlation between learning variables and drug consumption patterns, depression, and personality traits emerged for harm avoidance and positive learning in controls. CONCLUSIONS: Impaired transfer performance suggests that ADP had problems applying their acquired knowledge in a new context. Potential relations to dysfunctions of specific brain structures and implications of the finding for therapy are discussed.