Biomedical subjects

Brenda A Kirchhoff

Publications and source records attributed to Brenda A Kirchhoff.

4 recordsLinked to original sources

PubMed2006

Functional-anatomic correlates of individual differences in memory.

Memory abilities differ greatly across individuals. To explore a source of these differences, we characterized the varied strategies people adopt during unconstrained encoding. Participants intentionally encoded object pairs during functional MRI. Principal components analysis applied to a strategy questionnaire revealed that participants variably used four main strategies to aid learning. Individuals' use of verbal elaboration and visual inspection strategies independently correlated with their memory performance. Verbal elaboration correlated with activity in a network of regions that included prefrontal regions associated with controlled verbal processing, while visual inspection correlated with activity in a network of regions that included an extrastriate region associated with object processing. Activity in regions associated with use of these strategies was also correlated with memory performance. This study reveals functional-anatomic correlates of verbal and perceptual strategies that are variably used by individuals during encoding. These strategies engage distinct brain regions and may separately influence memory performance.

Adolescent↗

PubMed2005

Common and dissociable activation patterns associated with controlled semantic and phonological processing: evidence from FMRI adaptation.

Recent evidence suggests specialization of anterior left inferior prefrontal cortex (aLIPC; approximately BA 45/47) for controlled semantics and of posterior LIPC (pLIPC; approximately BA 44/6) for controlled phonology. However, the more automated phonological tasks commonly used raise the possibility that some of the typically extensive aLIPC activation during semantic tasks may relate to controlled language processing beyond the semantic domain. In the present study, an event-related fMRI adaptation paradigm was employed that used a standard controlled semantic task and a phonological task that also emphasized controlled processing. When compared with letter (baseline) processing, significant fMRI task and adaptation effects in the aLIPC and pLIPC regions ( approximately BA 45/47, approximately BA 44) were observed during both semantic and phonological processing, with aLIPC showing the strongest effects during semantic processing. A left frontal region ( approximately BA 6) showed task and relative adaptation effects preferential for phonological processing, and a left temporal region ( approximately BA 21) showed task and relative adaptation effects preferential for semantic processing. Our results demonstrate that aLIPC and pLIPC regions are involved in controlled processing across multiple language domains, arguing against a domain-specific LIPC model and for domain-preferentiality in left posterior frontal and temporal regions.

Adaptation, Physiological↗

PubMed2005

Orthographic distinctiveness and semantic elaboration provide separate contributions to memory.

Orthographic distinctiveness and semantic elaboration both enhance memory. The present behavioral and functional magnetic resonance imaging (fMRI) studies examined the relationship between the influences of orthographic distinctiveness and semantic elaboration on memory, and explored whether they make independent contributions. As is typical for manipulations of processing levels, words studied during semantic encoding were better remembered than words studied during nonsemantic encoding. Notably, orthographically distinct words were better recalled and received more remember responses on recognition memory tests than orthographically common words regardless of encoding task, suggesting that orthographic distinctiveness has an additive effect to that of semantic elaboration on memory. In the fMRI study, orthographic distinctiveness and semantic elaboration engaged separate networks of brain regions. Semantic elaboration modulated activity in left inferior prefrontal and lateral temporal regions. In contrast, orthographic distinctiveness modulated activity in distinct bilateral inferior prefrontal, extrastriate, and parietal regions. Orthographic distinctiveness and semantic elaboration appear to have separate behavioral and functional-anatomic contributions to memory.

Acoustic Stimulation↗

PubMed2004

Blockade of central cholinergic receptors impairs new learning and increases proactive interference in a word paired-associate memory task.

Experimental data and computational models suggest that blockade of muscarinic cholinergic receptors impairs paired-associate learning and increases proactive interference (E. DeRosa & M. E. Hasselmo, 2000; M. E. Hasselmo & J. M. Bower, 1993). The results presented here provide evidence in humans supporting these hypotheses. Young healthy subjects first learned baseline word pairs (A-B) and, after a delay, learned additional overlapping (A-C) and nonoverlapping (D-E) word pairs. As predicted, when compared with subjects who received the active placebo glycopyrrolate (4 microg/kg) and subjects who were not injected, those who received scopolamine (8 microg/kg) showed (a) overall impairment in new word paired-associate learning, but no impairment in cued recall of previously learned associates; and (b) greater impairment in learning overlapping (A-C) compared with nonoverlapping (D-E) paired associates.

Adolescent↗