Norepinephrine and acetylcholine mediation of the components of reflexive attention: implications for attention deficit disorders.

Attention deficit hyperactivity disorders (ADHD) create major learning barriers for children and significant social and legal handicaps for adults worldwide. Important advances in the genetic basis of the disease have been made, but reliable, biological, diagnostic markers remain elusive. This review takes the position that future progress in treating the core symptom of attention deficits requires a clearer understanding of the neuroscience of attention in normal individuals. Two important achievements in this direction have been the development of tasks that identify activity in the orienting, alerting and conflict networks, and the identification of neurotransmitters that mediate these components. The proven ability of these tasks to identify and characterize response components of "normal" attention argues that they could be used advantageously with patient populations. The categorization of neurotransmitter abnormalities in those with ADHD could clarify whether attention deficits occur within or across attention networks. To realize these goals, we evaluate laboratory studies of attention in humans and animals that address the underlying neurotransmitter systems, primarily norepinephrine and acetylcholine. We propose that key facts about deficits in reflexive and voluntary attention may be understood by a model that includes deficits in brain norepinephrine release and its effects on cholinergic activity in the parietal cortex.

Visual sensitivity to orientation of rectangles in mice with retinal degeneration.

C3H/HeJ male mice, an inbred strain showing retinal degeneration (rd), and normal-eyed DBA/IJ male mice were studied in a task requiring discrimination of horizontally and vertically oriented rectangles. The apparatus was modified Yerkes discrimination apparatus. The mice were given 30 days of discrimination training, 10 trials/day, after which 10 more trails were given on the 31st day with positive and negative cues reversed. Both strains showed a highly significant decrease in errors during acquisition, the rd strain making significantly fewer errors than the DBA/IJ animals. Reversal of the cues brought about a sharp increase in percentage of errors.