1999 |
Dobbins, Ian G |
R03Activity Code Description: To provide research support specifically limited in time and amount for studies in categorical program areas. Small grants provide flexibility for initiating studies which are generally for preliminary short-term projects and are non-renewable. |
Amnesia and Recog--Single Versus Multiprocess Models @ University of California Davis
Recently, it has been proposed that cortical regions in the inferior temporal lobe support recognition based on discriminations of stimulus familiarity, and that this function is independent of the hippocampal formation. The framing of recognition as a familiarity discrimination process has a long cognitive history, and was formalized with the application of signal detection theory to recognition data. However, many researchers have argued that this single process theory is insufficient because the conscious recollection of qualitative, contextual information can also be used during recognition judgments. Both animal and patient evidence suggest that this ability critically depends on the hippocampal formation. A dual process model, consistent with reports of preserved recognition in patients and animals, suggests that both the hippocampal formation and outlying regions contribute to recognition; the former critical for recollection, and the latter for familiarity discriminations. If correct, the preserved recognition in amnesics with circumscribed hippocampal damage, will be driven largely by item familiarity, and therefore will closely conform to the predictions of signal detection theory. For normal subjects, this is typically not the case, presumably because recollection also contributes to their performance. The current project will contrast controls and patients in four experiments in which the predicted trend of performance is different depending on whether recognition is a signal detection process, a discrete recollective process, or the result of both. If the hippocampal formation and outlying cortical regions perform a single, integrated memory process, then performance of amnesics should simply resemble a degraded version of controls. Such findings would be consistent with the declarative memory model, and recent single process accounts of recognition. However, if the hippocampal formation primarily serves recollection, then the pattern of preserved recognition in patients should qualitatively differ from controls. Such a finding would provide a neurological footing for dual process theory, help clarify the nature of preserved recognition in amnesics, and highlight the inadequacy of single factor memory estimates (e.g., d', percent correct, hits minus false alarms) for identifying functional deficits in amnesia.
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0.928 |
2006 — 2010 |
Dobbins, Ian G |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Functional Neuroimaging of Strategic Retrieval Processes
[unreadable] DESCRIPTION (provided by applicant): Episodic remembering critically relies on the generation retrieval plans, the elaborative processing of retrieval probes, the resolution of interference, and the monitoring of the sufficiency of memory with respect to decision criteria. Although prefrontal cortex (PFC) is the favored candidate for these mechanisms, regional and hemispheric localization for these mechanisms is unclear. Using a component-process model we will: (1) Determine whether left PFC is critically involved in formulating episodic retrieval plans. Recent research contrasting context and item memory have consistently identified left PFC and indicated that activity is not dependent on success, suggesting that it is the intent to retrieve contextual information that is critical. Here we intend to separate cue/question and probe dependent activity and determine whether these regions respond to non-verbalizable probes during contextually based retrieval demands. (2) Conduct Decision Theory based manipulations of memory decision criteria. By manipulating the number, location, and quality of decision criteria we will isolate PFC regions critical for implementing decision rules to memory content. (3) Investigate hemispheric asymmetries during episodic retrieval. Recent evidence suggests hemispheric asymmetries in PFC (particularly dorsal and polar) with left regions associated with contextually specific source attribution, and homologous right PFC regions showing relative increases during judgments of item recency or frequency, which are potentially based on global familiarity assessment. By directly contrasting recency, frequency, and context retrieval for matched materials within subjects, we will test whether the hemispheres are involved in fundamentally different aspects of memory retrieval, advancing beyond earlier constructs such as "effort" or "difficulty". Neurological changes during healthy aging and neurological disorders (e.g., Alzheimer's Dementia, Mild Cognitive Impairment, Traumatic Brain Injury) severely impact memory performance. However, because the control or decision processes regulating memory expression are poorly understood, behavioral impairments could often result from damage to systems that represent or store memory evidence, systems responsible for imposing decisions upon that content, or some combination of the 2. Determining how PFC regions normally regulate the translation of memory content into decisions or actions is therefore critical in understanding the memory performance decline in the above populations. [unreadable] [unreadable] [unreadable]
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0.958 |