RESUMO
Survivors of breast and other cancers often report protracted difficulty in performing tasks involving concentration and memory, even years after the completion of treatment. The current study investigated whether cancer and treatment history is associated with deficits in sensory filtering (gating out) and sensory memory (gating in), early processes in stimulus processing that may contribute to difficulties in later remembering. A group of breast cancer survivors and age-matched healthy control participants (mean age 54 years) underwent testing with paired-click and oddball tasks while electroencephalographic (EEG) signals were recorded. The survivors showed relatively poor inhibition of redundant sensory stimulation (P50 suppression). Dipole source analysis localized the survivors' impairment to the hippocampus, with preservation of function in gating mechanisms of the frontal lobe and auditory cortex. Survivors also showed disruption to sensory memory processes needed to register novel information in an otherwise uniform auditory environment (mismatch negativity). The findings suggest that survivors experience deficits in early, automatic mechanisms of sensory gating, which may trigger a cascade of later perceived attentional and memory deficits. If our account is accurate, ideal therapies might aim to restore early inhibitory processes, such as those gauged by P50 suppression.
Assuntos
Neoplasias da Mama , Sobreviventes de Câncer , Estimulação Acústica , Eletroencefalografia , Potenciais Evocados Auditivos , Humanos , Pessoa de Meia-Idade , Filtro Sensorial , SobreviventesRESUMO
Express saccadic eye movements are saccades of extremely short latency. In monkey, express saccades have been shown to occur much more frequently when the monkey has been trained to make saccades in a particular direction to targets that appear in predictable locations. Such results suggest that express saccades occur in large number only under highly specific conditions, leading to the view that vector-specific training and motor preparatory processes are required to make an express saccade of a particular magnitude and direction. To evaluate this hypothesis in humans, we trained subjects to make saccades quickly to particular locations and then examined whether the frequency of express saccades depended on training and the number of possible target locations. Training significantly decreased saccade latency and increased express saccade production to both trained and untrained locations. Increasing the number of possible target locations (two vs. eight possible targets) led to only a modest increase of saccade latency. For most subjects, the probability of express saccade occurrence was much higher than that expected if vector-specific movement preparation were necessary for their production. These results suggest that vector-specific motor preparation and vector-specific saccade training are not necessary for express saccade production in humans and that increases in express saccade production are due in part to a facilitation in fixation disengagement or else a general enhancement in the ability of the saccadic system to respond to suddenly appearing visual stimuli.