An fMRI investigation of the effects of attempted naming on word retrieval in aphasia

In healthy controls, picture naming performance can be facilitated by a single prior exposure to the same picture ("priming"). This priming phenomenon is utilized in the treatment of aphasia, which often includes repeated picture naming as part of a therapeutic task. The current study sought to determine whether single and/or multiple exposures facilitate subsequent naming in aphasia and whether such facilitatory effects act through normal priming mechanisms. A functional magnetic resonance imaging paradigm was employed to explore the beneficial effects of attempted naming in two individuals with aphasia and a control group. The timing and number of prior exposures was manipulated, with investigation of both short-term effects (single prior exposure over a period of minutes) and long-term effects (multiple presentations over a period of days). Following attempted naming, both short-term and long-term facilitated items showed improvement for controls, while only the long-term condition showed benefits at a behavioral level for the participants with aphasia. At a neural level, effects of long-term facilitation were noted in the left precuneus for one participant with aphasia, a result also identified for the equivalent contrast in controls. It appears that multiple attempts are required to improve naming performance in the presence of anomia and that for some individuals with aphasia the source of facilitation may be similar to unimpaired mechanisms engaged outside the language network

The basal ganglia circuits, dopamine, and ambiguous word processing: A neurobiological account of priming studies in Parkinson's disease

Research into the processing of lexical ambiguities has provided a valuable paradigm for investigating the functional architecture of the language processing system in normal and neurologically impaired populations and specifically, how basal ganglia circuits and the neurotransmitter dopamine may act to enhance and/or suppress various meanings relative to the context in which the lexical ambiguity appears. In this review, we develop the hypothesis that an integrated basal ganglia thalamocortical circuit linking the striatum and inferior frontal cortex is involved in the enhancement and suppression of ambiguous word meanings when a lexical ambiguity is presented within a linguistic context. Reference to behavioral, neurophysiological, and neurochemical studies of subcortical function in both healthy populations and people with Parkinson's disease will be used to provide further support for the proposal that the subcortex is integrally involved in ambiguous word processing. (JINS, 2008, 14, 351–364.

A neurophysiological study of semantic processing in Parkinson’s disease

Objectives: Cognitive-linguistic impairments in Parkinson's disease (PD) have been well documented; however, few studies have explored the neurophysiological underpinnings of semantic deficits in PD. This study investigated semantic function in PD using event-related potentials. Methods: Eighteen people with PD and 18 healthy controls performed a semantic judgement task on written word pairs that were either congruent or incongruent. Results: The mean amplitude of the N400 for new incongruent word pairs was similar for both groups, however the onset latency was delayed in the PD group. Further analysis of the data revealed that both groups demonstrated attenuation of the N400 for repeated incongruent trials, as well as attenuation of the P600 component for repeated congruent trials. Conclusions: The presence of N400 congruity and N400 repetition effects in the PD group suggests that semantic processing is generally intact, but with a slower time course as evidenced by the delayed N400. Additional research will be required to determine whether N400 and P600 repetition effects are sensitive to further cognitive decline in PD

The Suppression of Irrelevant Semantic Representations in Parkinson’s Disease

The impairment of lexical-semantic inhibition mechanisms in Parkinson’s disease (PD) remains a source of contention. In order to observe whether people with PD are able to suppress irrelevant semantic information during picture naming, the present study employed an object-based negative priming paradigm with 16 participants with PD and 13 healthy controls. The task required participants to name a red target image while ignoring a superimposed, green distractor image. The semantic relationship between the distractor image and the target image of the subsequent trial was manipulated, such that the distractor image was identical, semantically related, or semantically unrelated to said target image. The PD group and the control group were slower in naming a target image that had previously served as a distractor image, relative to naming a target image that was unrelated to the previous distractor image. Thus, a negative priming effect was present in both groups. Furthermore, no significant difference in the magnitude of this effect was observed between the control and PD groups. When considered in the context of existing literature surrounding negative priming in PD, these results suggest that inhibition is subserved by multiple, domain-specific mechanisms and that the inhibitory processing of visual-semantic stimuli is intact in PD

Priming Picture Naming with a Semantic Task: An fMRI Investigation

Prior semantic processing can enhance subsequent picture naming performance, yet the neurocognitive mechanisms underlying this effect and its longevity are unknown. This functional magnetic resonance imaging study examined whether different neurological mechanisms underlie short-term (within minutes) and long-term (within days) facilitation effects from a semantic task in healthy older adults. Both short- and long-term facilitated items were named significantly faster than unfacilitated items, with short-term items significantly faster than long-term items. Region of interest results identified decreased activity for long-term facilitated items compared to unfacilitated and short-term facilitated items in the mid-portion of the middle temporal gyrus, indicating lexical-semantic priming. Additionally, in the whole brain results, increased activity for short-term facilitated items was identified in regions previously linked to episodic memory and object recognition, including the right lingual gyrus (extending to the precuneus region) and the left inferior occipital gyrus (extending to the left fusiform region). These findings suggest that distinct neurocognitive mechanisms underlie short- and long-term facilitation of picture naming by a semantic task, with long-term effects driven by lexical-semantic priming and short-term effects by episodic memory and visual object recognition mechanisms

The neural correlates of picture naming facilitated by auditory repetition

Background: Overt repetition of auditorily presented words can facilitate picture naming performance in both unimpaired speakers and individuals with word retrieval difficulties, but the underlying neurocognitive mechanisms and longevity of such effects remain unclear. This study used functional magnetic resonance imaging to examine whether different neurological mechanisms underlie short-term (within minutes) and long-term (within days) facilitation effects from an auditory repetition task in healthy older adults

Data for Parkinson's disease lexical ambiguity research

Contains demographics, cognitive test scores and event-related potential dat

Recall and Recognition data for the novel word learning in white noise research.

Recall data for each group, condition (name/semantic) and trial (1-5). Final recognition data for each condition and the ANT 'conflict effect'

Cognitive plasticity in Parkinson's disease

Parkinson’s disease (PD) is a neurodegenerative condition traditionally associated with dopamine loss and impaired motor function. However, it is now well recognized that PD is also associated with a range of cognitive deficits that increase with disease progression. While increasing non-dopaminergic pathology over time may account for some cognitive deficits, there is now considerable evidence for cognitive plasticity in PD in response to neuromodulation via deep brain stimulation and dopaminergic interventions, in addition to more preliminary work regarding behavioral treatments of cognitive deficits in PD. Recent work suggests that functional plasticity, upregulation within frontostriatal circuits, and broader network changes beyond the dopaminergic system are likely neural mechanisms underpinning cognitive plasticity in PD