Steven W. Anderson

In some neurological syndromes, acquired personality disturbances are the veritable sine qua non of the condition. Several instruments have been used to evaluate personality changes, and to provide...

Better understanding of the processes by which dysfunction in prefrontal circuitry leads to impaired decision-making remains a fundamental challenge for cognitive neuroscience. Poor decision-making...

The number of people diagnosed with Alzheimer’s disease (AD), a progressive and terminal kind of dementia, continues to rise with an estimated 14 million Americans affected by 2050. Prior to an AD diagnosis, many individuals are diagnosed with mild cognitive impairment (MCI) and have similar, but less severe, symptoms as those with AD. A common occurrence in even the early stages of AD is word finding deficits, which significantly impact effective communication. Semantic priming studies have shown that word finding deficits in AD may partly be due to limitations in the automaticity of semantic retrieval. However, it is unknown if the automaticity of semantic retrieval underlies word finding difficulties in individuals with MCI or if the deficit in semantic retrieval occurs later in the AD continuum. The current study uses semantic priming to examine the extent to which semantic retrieval is automatic in individuals with MCI in four categories: distinctive attributes (e.g., zebra – stripe), shared attributes (e.g., pigeon – wing), category coordinates (e.g., cat – dog), and abstract words with neutral arousal levels (e.g., motive – reason). Experiments 1 and 2 establish our stimuli in a group of healthy younger and older adults, respectively. Experiment 3 directly compares semantic retrieval in healthy older adults and a group of individuals with MCI. The results demonstrate that individuals with MCI only show priming on shared attributes when evaluating the raw data. When the data were transformed to control for slowing (a commonly utilized strategy because individuals with MCI are known to have both slower response times and executive functioning deficits), individuals with MCI exhibited priming in three of the four categories (shared attributes, category coordinates and abstract words) which was identical to the healthy older adults in Experiment 2. We found priming for distinctive attributes only in the healthy younger adults. Finally, an exploratory analysis showed individuals with MCI and an additional diagnosis did not exhibit significant priming in any category while those individuals with MCI alone showed priming effects for shared attributes and category coordinates. These findings suggest individuals with MCI exhibit functional automaticity of semantic retrieval on a broad range of word types. However, the presence of additional neurological and/or psychological conditions (not including dementia) negatively impacts the automaticity of semantic retrieval.

Human subjects play an important role in scientific research. Studying individuals with cognitive impairments is critical for advancing knowledge and treatment for diseases that cause cognitive impairments, including dementia and schizophrenia. Those with cognitive impairments may lack the capacity or ability to provide informed consent to research participation, and it is unknown how specific cognitive impairments impact consent capacity. This study examined how impaired cognition impacts the consent process. Normal healthy adults and patients with impairments in memory, language, or executive functions read fictional research studies. Consent capacity was measured with either the MacArthur Competence Assessment Tool for Clinical Research or the Iowa Consent Tool (ICT), described and developed in this study. Patients with memory or executive function impairments showed lower understanding scores than normal comparisons. However, these patient groups did not differ from each other. Patients with impaired executive functions did not have lower appreciation or reasoning scores when compared with normal comparisons. Participant appreciation and reasoning varied between different research scenarios, suggesting that there may be underlying characteristics of studies that could be challenging for participants. Further investigation into the roles of language complexity and the levels of cost and gain may clarify these differences. This first use of the ICT suggests that it may provide useful measures of consent appreciation that should be developed. Future research should examine targeted interventions to improve the consent process. This research has important implications for consent with both cognitively impaired patients and healthy adults in other applications including medical treatment.

The neural basis of language has been studied for centuries, yet the networks critically involved in simply identifying or understanding a spoken word remain elusive. Several functional-anatomical models of critical neural substrates of receptive speech have been proposed, including (1) auditory-related regions in the left mid-posterior superior temporal lobe, (2) motor -related regions in the left frontal lobe (in normal and/or noisy conditions), the left anterior superior temporal lobe, or (4) bilateral mid-posterior superior temporal areas. One difficulty in comparing these models is that they often focus on different aspects of the sound-to-meaning pathway and are supported by different types of stimuli and tasks. Two auditory tasks that are typically used in separate studies—syllable discrimination and word comprehension—often yield different conclusions. We assessed syllable discrimination (words and nonwords) and word comprehension (clear speech and with a noise masker) in 158 individuals with focal brain damage: left (n=113) or right (n=19) hemisphere stroke, left (n=18) or right (n=8) anterior temporal lobectomy, and 26 neurologically-intact controls. Discrimination and comprehension tasks are doubly dissociable both behaviorally and neurologically. In support of a bilateral model, clear speech comprehension was near ceiling in 95% of left stroke cases and right temporal damage impaired syllable discrimination. Lesion-symptom mapping analyses for the syllable discrimination and noisy word comprehension tasks each implicated most of the left superior temporal gyrus (STG). Comprehension but not discrimination tasks also implicated the left pMTG, while discrimination but not comprehension tasks also implicated more dorsal sensorimotor regions in posterior perisylvian cortex.

Damage to the ventromedial prefrontal cortex (vmPFC) can lead to disturbances in personality, emotional dysregulation, impairments in social conduct, and difficulties in decision-making. Many researchers have likened the conduct of individuals with vmPFC lesions to that of criminal psychopaths, labeling the effects of vmPFC damage “pseudopsychopathy” or “acquired sociopathy.” However, although psychopathy—a condition marked by a distinct mosaic of antisocial personality traits and behaviors—has been studied and characterized as a psychological and behavioral disorder by many researchers, the overlap between acquired sociopathy and psychopathy remains ambiguous. This study assessed the severity of psychopathic personality traits in neurological patients with acquired damage to the vmPFC using both informant-report and self-report measures. On both informant-report and self-report measures, individuals with vmPFC damage showed no significant elevations across a wide range of psychopathic traits relative to demographically-matched neurologically healthy comparison participants and patients with damage outside of the vmPFC. The results showed only one trait, Fearlessness, that was significantly higher in patients with vmPFC lesions relative to the neurologically-healthy comparison group.

Semantic memory includes vocabulary and word meanings, conceptual information, and general facts about the world (Tulving, 1972). According to the standard view of semantic memory in cognitive neuroscience, the hippocampus is necessary to first acquire new semantic information (Gabrieli, Cohen, & Corkin, 1988), but these representations are then consolidated in the neocortex and become independent of the hippocampus with time (McClelland, McNaughton, & O'Reilly, 1995). Remote semantic memory is considered independent of the hippocampus, and the hippocampus is not thought to play a critical role in the processing and use of such representations. The current work challenges the notion that previously acquired semantic knowledge, and its use during communication, is independent of the hippocampus. A group of patients with bilateral hippocampal damage and severe impairments in declarative memory were tested. Intact naming and word-definition matching performance in amnesia, has led to the notion that remote semantic memory is intact in patients with hippocampal amnesia. Motivated by perspectives of word learning as a protracted process where additional features and senses of a word are added over time, and by recent discoveries about the time course of hippocampal contributions to on-line relational processing, reconsolidation, and the flexible integration of information, we revisit the notion that remote semantic memory is intact in amnesia. Using measures of semantic richness and vocabulary depth from psycholinguistics and first and second language-learning studies, we examined how much information is associated with previously acquired, highly familiar words in hippocampal amnesic patients. Relative to healthy demographically matched comparison participants and a group of brain-damaged comparison participants, the patients with hippocampal amnesia performed significantly worse on both productive and receptive measures of vocabulary depth and semantic richness. In the healthy brain, semantic memory appears to get richer and deeper with time. Healthy participants of all ages were tested on these measures and strong correlations are seen with age as older healthy adults displayed richer semantic knowledge than the younger adults. The patient data provides a mechanism: hippocampal relational binding supports the deepening and enrichment of knowledge over time. These findings suggest that remote semantic memory is impoverished in patients with hippocampal amnesia and that the hippocampus supports the maintenance and updating of semantic memory beyond its initial acquisition. The use of lexical and semantic knowledge during discourse was also examined. Amnesic patients displayed significantly lower levels of lexical diversity in the speech they produced, and showed a strong trend toward producing language with reduced levels of semantic detail suggesting that patients cannot use their semantic representations as richly during communication. These results add to a growing body of work detailing a role for the hippocampus in language processing more generally. By documenting a role for the hippocampus in maintaining, updating, and using semantic knowledge, this work informs theories of semantic memory and it's neural bases, advances knowledge of the role of the hippocampus in supporting human behavior, and brings more sensitive measures to the neuroscientific study of semantic memory.