Orbitofrontal cortex and dynamic filtering of emotions

Authors:

• Randall R. Rule

• Arthur P. Shimamura

• Robert T. Knight

Date: 2002

PubMed: 12775190

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Abstract:

Event-related potentials (ER) were recorded in response to mildly aversive somatosensory and auditory stimuli. Patients with orbitofrontal lesions exhited enhanced ERPs (i.e., P3 amplitudes), as compared with control subjects. Moreover, these patients did not habituate to somatoensory stimuli across blocks of trials. The results were specific to orbitofrontal damage, since patients with damage to the dorsolateral prefontal cortex did not exhibit enhanced P3 amplitudes. These findings suggest damage to the orbitofrontal cortex impairs the ability to modulate or inhibit neural responses to aversive stimuli. The findings are couched in terms of dynamic filtering theory, which suggests that the orbitofrontal cortex is involved in the selection and active inhibition of neural circuits associated with emotional responses.

Impaired word-stem priming in patients with temporal-occipital lesions

Authors:

• Lynn Nielsen-Bohlman

• Michael Ciranni

• Arthur P. Shimamura

• Robert T. Knight

Date: 1997

PubMed: 9256373

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Abstract:

In the word-stem priming test, words are presented (e.g., MOTEL, PARADE), and later subjects are shown three-letter word stems (e.g., MOT, PAR) and asked to complete each stem with the first word that comes to mind. Word-stem priming, as well as other aspects of implicit memory, are intact in amnesic patients with medial temporal lesions. However, this form of priming has been shown to be impaired in patients with Alzheimer's disease, suggesting that damage to neocortical areas outside the medial temporal lobe contributes to impaired priming in these patients. To examine the role of posterior cortical areas on word-stem priming, we administered the test to patients with unilateral temporal-occipital lesions. Patients with temporal-occipital lesions exhibited significantly impaired priming on this test. The findings suggest a critical role of the inferior posterior neocortex in the expression of this form of implicit memory.

Impaired retrieval from remote memory in patients with frontal lobe damage

Authors:

• Jennifer A. Mangels

• Felicia B. Gershberg

• Arthur P. Shimamura

• Robert T. Knight

Date: 1996

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Abstract:

Patients with unilateral dorsolateral frontal lobe lesions and matched controls were given 2 tests of remote memory for public information, the Public Events Test and the Famous Faces Test. On both tests, the patients with frontal lobe lesions exhibited impaired recall for remote information. Recognition memory was relatively preserved. Provision of semantic and phonemic cues in the Famous Faces Test did not completely compensate for their recall deficit. These findings suggest that the remote memory impairment exhibited by frontal patients may be related to deficits in strategic search of memory. These deficits in retrieval from remote memory extend the array of memory deficits associated with damage to the frontal lobes.

Susceptibility to memory interference effects following frontal lobe damage: findings from tests of paired-associate learning.

Authors:

• Arthur P. Shimamura

• Paul J. Jurica

• Jennifer A. Mangels

• Felicia B. Gershberg

• Robert T. Knight

Date: 1995

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Abstract:

Patients with frontal lobe lesions were administered tests of paired-associate learning in which cue and response words are manipulated to increase interference across two study lists. In one test of paired-associate learning (AB-AC test), cue words used in one list are repeated in a second list but are associated with different response words (e.g., LION-HUNTER, LION-CIRCUS). In another test (AB-ABr test), words used in one list are repeated in a second list but are rearranged to form new pairs. Compared to control subjects, patients with frontal lobe lesions exhibited disproportionate impairment of second-list learning as a result of interference effects. In particular, patients exhibited the poorest performance during the initial trial of the second list, a trial in which interference effects from the first list would be most apparent. These findings suggest that the on-line control of irrelevant or competing memory associations is disrupted following frontal lobe lesions. This disruption may be indicative of an impaired gating or filtering mechanism that affects not only memory function but other cognitive function as well.

Susceptibility to memory interference effects following frontal lobe damage: findings from tests of paired-associate learning

Authors:

• Arthur P. Shimamura

• Paul J. Jurica

• Jennifer A. Mangels

• Felicia B. Gershberg

• Robert T. Knight

Date: 1995

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Abstract:

Patients with frontal lobe lesions were administered tests of paired-associate learning in which cue and response words are manipulated to increase interference across two study lists. In one test of paired-associate learning (AB-AC test), cue words used in one list are repeated in a second list but are associated with different response words (e.g., LION-HUNTER, LION-CIRCUS). In another test (AB-ABr test), words used in one list are repeated in a second list but are rearranged to form new pairs. Compared to control subjects, patients with frontal lobe lesions exhibited disproportionate impairment of second-list learning as a result of interference effects. In particular, patients exhibited the poorest performance during the initial trial of the second list, a trial in which interference effects from the first list would be most apparent. These findings suggest that the on-line control of irrelevant or competing memory associations is disrupted following frontal lobe lesions. This disruption may be indicative of an impaired gating or filtering mechanism that affects not only memory function but other cognitive function as well.

Cognitive neuropsychology is more than single-case studies

Authors:

• Lynn C. Robertson

• Robert T. Knight

• Robert Rafal

• Arthur P. Shimamura

Date: 1993

PubMed: 8347215

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Abstract:

S. M. Sokol et al. (1991) claim that "The Cognitive Neuropsychology Approach" (p. 355) is limited to the single-case study design. The present article takes issue with this claim. Contrary to the beliefs of Sokol et al., we argue (a) that cognitive modularity is best studied by group design, (b) that the possibility of neural reorganization in patients should be tested through converging evidence from different populations using various methods, and (c) that cognitive neuropsychology can benefit from being a part of cognitive neuroscience where both neural and cognitive mechanisms underlying normal cognition are relevant.

Intact implicit memory in patients with frontal lobe lesions

Authors:

• Arthur P. Shimamura

• Felicia B. Gershberg

• Paul J. Jurica

• Jennifer A. Mangels

• Robert T. Knight

Date: 1992

PubMed: 1436439

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Abstract:

Patients with frontal lobe lesions and control subjects were administered tests of word-stem completion priming. In this implicit memory test, subjects are first presented words (e.g. MOTEL, PARADE) in an incidental learning paradigm. Following word presentation, subjects are shown word stems (e.g. MOT, PAR) and asked to produce the first word that comes to mind. Patients with frontal lobe lesions exhibited normal levels of word-stem completion. These findings indicate that implicit memory can operate normally despite damage to the prefrontal cortex. The present results substantiate previous neuropsychological and positron emission tomography findings which indicate that word priming depends critically on posterior cortical areas.