Biomedical subjects

A J Senkfor

Publications and source records attributed to A J Senkfor.

4 recordsLinked to original sources

PubMed2000

Electrophysiological dissociation between verbal and nonverbal semantic processing in learning disabled adults.

Event-related potentials (ERPs) were recorded as 16 adults with learning disabilities (LD) and 16 controls were presented with two sets of stimuli. The first set comprised pairs of line drawings and environmental sounds (nonverbal condition); the second consisted of printed and spoken words (verbal condition). In the controls, semantically related items elicited smaller N400s than unrelated items in both conditions, with opposing hemispheric asymmetries for spoken words and environmental sounds. The LD group did not show a significant difference between related and unrelated words, despite a robust context effect for nonspeech sounds. The results suggest anomalous processing limited to the verbal domain in a simple semantic association task in the LD group. Semantic deficits in this group may reflect a relatively specific deficit in forming verbal associations rather than a more general difficulty that spans both verbal and nonverbal domains.

Adolescent↗

PubMed2000

Memory for drawings in locations: spatial source memory and event-related potentials.

Event-related potentials (ERPs) were recorded during recognition tasks for line drawings (items) or for both drawings and their spatial locations (sources). Recognized drawings elicited more positive ERPs than new drawings. Independent of accuracy in the spatial judgment, the old/new effect in the source recognition task was larger over the prefrontal scalp, and of longer temporal duration than in the item recognition task, suggesting that the source memory task engaged a qualitatively distinct memory process. More posterior scalp sites were sensitive to the accuracy of the source judgment, but this effect was delayed relative to the difference between studied and unstudied drawings, suggesting that source memory processes are completed after item recognition. Similarities and differences between spatial source memory and memory for conjunctions of other stimulus attributes are discussed, together with the role of prefrontal cortex in memory.

Adult↗

PubMed1998

Who said what? An event-related potential investigation of source and item memory.

Event-related potentials (ERPs) were recorded during recognition tasks for spoken words alone (items) or for both words and the voice of the speaker (sources). Neither performance nor ERP measures suggested that voice information was retrieved automatically during the item-recognition task. In both tasks, correctly recognized old words elicited more positive ERPs than new words, beginning around 400 ms poststimulus onset. In the source task only, old words also elicited a focal prefrontal positivity beginning about 700 ms. The prefrontal task effect did not distinguish trials with accurate and inaccurate voice judgments and is interpreted as reflecting the search for voice information in memory. More posterior recording sites were sensitive to the successful recovery of voice or source information. The results indicate that word and voice information were retrieved hierarchically and distinguish retrieval attempt from retrieval success.

Adult↗

PubMed1996

Memory for words and novel visual patterns: repetition, recognition, and encoding effects in the event-related brain potential.

Event-related potentials (ERPs) were recorded during initial study and recognition of words and novel visual patterns. Words and patterns yielded similar recognition results that discriminated correctly recognized old items from correct new items, incorrect old items, and incorrect new items. The study phase data included a number of dissociations between words and patterns. Occasional repeated items yielded faster reaction times for both stimulus types but a late positive ERP repetition effect for words only. The study phase data differentiated words that would later be recognized versus unrecognized, but the patterns did not yield a similar encoding effect. Moreover, the study phase positivity contingent on subsequent recognition was restricted to words that received a positive semantic judgment during study. The functional relationships among the repetition, recognition, and encoding effects are discussed.

Adult↗