Selective attentional processing and the right hemisphere: effects of aging and alcoholism.

Thirty-seven nonalcoholic individuals (22 women, 15 men), ages 26-76, and 36 abstinent alcoholic individuals (11 women, 25 men), ages 31-74, participated in a cued-detection task that assessed right hemisphere (RH) functioning associated with aging and alcoholism. Young controls were less reliant on cues following RH activation, which is consistent with the view that the RH has an advantage because it has the ability to attend to a broader spatial array than does the left hemisphere (LH). This RH advantage was not obtained in older controls or alcoholic participants. The pattern of results for the older nonalcoholic participants indicated that they neither benefited from valid cues following LH activation nor exhibited enhanced processing on invalid cue trials following RH activation. The results for the alcoholic participants were consistent with RH functional decline, but did not support the view that alcoholism and aging have synergistic effects.

Impairments of brain and behavior: the neurological effects of alcohol.

Chronic heavy drinking and alcoholism can have serious repercussions for the functioning of the entire nervous system, particularly the brain. These effects include changes in emotions and personality as well as impaired perception, learning, and memory. Neuropathological and imaging techniques have provided evidence of physical brain abnormalities in alcoholics, such as atrophy of nerve cells and brain shrinkage. At the cellular level, alcohol appears to directly affect brain function in a variety of ways, primarily by interfering with the action of glutamate, gamma-aminobutyric acid, and other neurotransmitters. Neurological disorders also can result from vitamin deficiency and liver disease, two health problems that commonly occur with alcoholism. Other hypotheses, based on factors such as aging, gender, and genetics, have been developed to explain various alcohol-related neurological consequences. Many pharmacological treatments to improve neuropsychological functioning in alcoholics have been tested, but none has proved entirely successful. With prolonged abstinence, however, slow recovery of cognitive functioning can occur in some cases.

The eccentricity effect: target eccentricity affects performance on conjunction searches.

The serial pattern found for conjunction visual-search tasks has been attributed to covert attentional shifts, even though the possible contributions of target location have not been considered. To investigate the effect of target location on orientation x color conjunction searches, the target's duration and its position in the display were manipulated. The display was present either until observers responded (Experiment 1), for 104 msec (Experiment 2), or for 62 msec (Experiment 3). Target eccentricity critically affected performance: A pronounced eccentricity effect was very similar for all three experiments; as eccentricity increased, reaction times and errors increased gradually. Furthermore, the set-size effect became more pronounced as target eccentricity increased, and the extent of the eccentricity effect increased for larger set sizes. In addition, according to stepwise regressions, target eccentricity as well as its interaction with set size were good predictors of performance. We suggest that these findings could be explained by spatial-resolution and lateral-inhibition factors. The serial self-terminating hypothesis for orientation x color conjunction searches was evaluated and rejected. We compared the eccentricity effect as well as the extent of the orientation asymmetry in these three conjunction experiments with those found in feature experiments (Carrasco & Katz, 1992). The roles of eye movements, spatial resolution, and covert attention in the eccentricity effect, as well as their implications, are discussed.