Attentional Functioning Following Striatal Lesions and Psychostimulants Administration

Many neuropsychiatric disorders are characterized by impaired ability to inhibit irrelevant information, e.g.: Schizophrenia, Alzheimer`s, OCD, Huntington`s, Parkinson`s, Attention disorders, etc. The ability to inhibit irrelevant external as well as internal stimuli seems to play a major role also in Attention Deficit Disorders (ADHD).

Over the past decade an increasing rate of children and adults diagnosed with ADHD and treated with Methylphenidate (Mph) has emerged; alongside to increasing reported drug abuse. Mph abuse can lead to long-term adverse consequences, though it has beneficial effects on ADHD symptoms. Therefore, a better understanding of the underlying mechanism of attention processing is medically important.

The striatum is a brain structure responsible for integrating sensorimotor, emotional and cognitive information, with an involvement in attention functions. The aim of the present study is to dissect the functional differences between striatal sub-regions in attention processing. For this purpose, rats surgically underwent the following striatal lesions: (I) Nucleus Accumbens, (II) Caudate Nucleus, (III) Putamen and (IV) Internal Capsule. Afterward rats were treated with the psychostimulants Mph or Methamphetamine (Mta), compared to saline. All rats were examined for changes in attention abilities using an overt and covert attention tests.

Results support functional differentiation between the striatal sub-regions and therefore indicate the existence of a sub-striatal underlying mechanism of attention functioning; regulated by the dopaminergic system as supported by the observed effects of Mph.