Asunto(s)
Enfermedades de los Párpados/diagnóstico , Granuloma/diagnóstico , Enfermedad Relacionada con Inmunoglobulina G4/complicaciones , Inmunoglobulina G/inmunología , Xantomatosis/diagnóstico , Biopsia , Diagnóstico Diferencial , Enfermedades de los Párpados/complicaciones , Granuloma/complicaciones , Humanos , Enfermedad Relacionada con Inmunoglobulina G4/inmunología , Imagen por Resonancia Magnética , Masculino , Persona de Mediana Edad , Xantomatosis/complicacionesRESUMEN
Early detection may be the key to developing therapies that will combat Alzheimer's disease (AD). It has been consistently demonstrated that one of the main pathologies of AD, tau, is present in the brain decades before a clinical diagnosis. Tau pathology follows a stereotypical route through the medial temporal lobe beginning in the entorhinal and perirhinal cortices. If early pathology leads to very subtle changes in behavior, it may be possible to detect these changes in subjects years before a clinical diagnosis can currently be made. We aimed to discover if cognitively normal middle-aged adults (40-60 years old) at increased risk for AD due to family history would have impaired performance on a cognitive task known to challenge the perirhinal cortex. Using an oddity detection task, we found that subjects with a family history of AD had lowered accuracy without demonstrating differences in rate of acquisition. There were no differences between subjects' medial temporal lobe volume or cortical thickness, indicating that the changes in behavior were not due to significant atrophy. These results demonstrate that subtle changes in perceptual processing are detectable years before a typical diagnosis even when there are no differences detectable in structural imaging data. Anatomically-targeted cognitive testing may be useful in identifying subjects in the earliest stages of AD.
Asunto(s)
Enfermedad de Alzheimer/complicaciones , Discriminación en Psicología/fisiología , Salud de la Familia , Trastornos de la Percepción/etiología , Reconocimiento en Psicología/fisiología , Adulto , Enfermedad de Alzheimer/diagnóstico por imagen , Enfermedad de Alzheimer/genética , Corteza Cerebral/diagnóstico por imagen , Femenino , Humanos , Imagen por Resonancia Magnética , Masculino , Persona de Mediana Edad , Pruebas Neuropsicológicas , Trastornos de la Percepción/diagnóstico por imagen , Trastornos de la Percepción/genética , Estimulación Luminosa , Detección de Señal PsicológicaRESUMEN
A growing body of literature has investigated changes in eye movements as a result of Alzheimer's disease (AD). When compared to healthy, age-matched controls, patients display a number of remarkable alterations to oculomotor function and viewing behavior. In this article, we review AD-related changes to fundamental eye movements, such as saccades and smooth pursuit motion, in addition to changes to eye movement patterns during more complex tasks like visual search and scene exploration. We discuss the cognitive mechanisms that underlie these changes and consider the clinical significance of eye movement behavior, with a focus on eye movements in mild cognitive impairment. We conclude with directions for future research.
Asunto(s)
Enfermedad de Alzheimer/fisiopatología , Movimientos Oculares/fisiología , Enfermedad de Alzheimer/complicaciones , Trastorno por Déficit de Atención con Hiperactividad/etiología , Trastornos del Conocimiento/etiología , Humanos , Estimulación Luminosa , Desempeño PsicomotorRESUMEN
Priming reflects an important means of learning that is mediated by implicit memory. Importantly, priming occurs for previously viewed objects (item-specific priming) and their category relatives (category-wide priming). Two distinct neural mechanisms are known to mediate priming, including the sharpening of a neural object representation and the retrieval of stimulus-response mappings. Here, we investigated whether the relationship between these neural mechanisms could help explain why item-specific priming generates faster responses than category-wide priming. Participants studied pictures of everyday objects, and then performed a difficult picture identification task while we recorded event-related potentials (ERP). The identification task gradually revealed random line segments of previously viewed items (Studied), category exemplars of previously viewed items (Exemplar), and items that were not previously viewed (Unstudied). Studied items were identified sooner than Unstudied items, showing evidence of item-specific priming, and importantly Exemplar items were also identified sooner than Unstudied items, showing evidence of category-wide priming. Early activity showed sustained neural suppression of parietal activity for both types of priming. However, these neural suppression effects may have stemmed from distinct processes because while category-wide neural suppression was correlated with priming behavior, item-specific neural suppression was not. Late activity, examined with response-locked ERPs, showed additional processes related to item-specific priming including neural suppression in occipital areas and parietal activity that was correlated with behavior. Together, we conclude that item-specific and category-wide priming are mediated by separate, parallel neural mechanisms in the context of the current paradigm. Temporal differences in behavior are determined by the timecourses of these distinct processes.
Asunto(s)
Potenciales Evocados/fisiología , Aprendizaje/fisiología , Memoria/fisiología , Desempeño Psicomotor/fisiología , Percepción Visual/fisiología , Adolescente , Adulto , Mapeo Encefálico/métodos , Femenino , Humanos , Masculino , Estimulación Luminosa/métodos , Reconocimiento en Psicología , Adulto JovenRESUMEN
The hippocampus creates distinct episodes from highly similar events through a process called pattern separation and can retrieve memories from partial or degraded cues through a process called pattern completion. These processes have been studied in humans using tasks where participants must distinguish studied items from perceptually similar lure items. False alarms to lures (incorrectly reporting a perceptually similar item as previously studied) are thought to reflect pattern completion, a retrieval-based process. However, false alarms to lures could also result from insufficient encoding of studied items, leading to impoverished memory of item details and a failure to correctly reject lures. The current study investigated the source of lure false alarms by comparing eye movements during the initial presentation of items to eye movements made during the later presentation of item repetitions and similar lures in order to assess mnemonic processing at encoding and retrieval, respectively. Relative to other response types, lure false alarms were associated with fewer fixations to the initially studied items, suggesting that false alarms result from impoverished encoding. Additionally, lure correct rejections and lure false alarms garnered more fixations than hits, denoting additional retrieval-related processing. The results suggest that measures of pattern separation and completion in behavioral paradigms are not process-pure.
Asunto(s)
Movimientos Oculares , Memoria , Reconocimiento Visual de Modelos , Desempeño Psicomotor , Señales (Psicología) , Medidas del Movimiento Ocular , Femenino , Fijación Ocular , Humanos , Masculino , Pruebas Neuropsicológicas , Estimulación Luminosa , Análisis y Desempeño de Tareas , Adulto JovenRESUMEN
Visual working memory (VWM) capacity is reduced in older adults. Research has shown age-related impairments to VWM encoding, but aging is likely to affect multiple stages of VWM. In the present study, we recorded the event-related potentials (ERPs) of younger and older adults during VWM maintenance and retrieval. We measured encoding-stage processing with the P1 component, maintenance-stage processing with the contralateral delay activity (CDA), and retrieval-stage processing by comparing the activity for old and new items (old-new effect). Older adults showed lower behavioral capacity estimates (K) than did younger adults, but surprisingly, their P1 components and CDAs were comparable to those of younger adults. This remarkable dissociation between neural activity and behavior in the older adults indicated that the P1 and CDA did not accurately assess their VWM capacity. However, the neural activity evoked during VWM retrieval yielded results that helped clarify the age-related differences. During retrieval, younger adults showed early old-new effects in frontal and occipital areas and a late central-parietal old-new effect, whereas older adults showed a late right-lateralized parietal old-new effect. The younger adults' early old-new effects strongly resembled an index of perceptual fluency, suggesting that perceptual implicit memory was activated. The activation of implicit memory could have facilitated the younger adults' behavior, and the lack of these early effects in older adults may suggest that they have much lower-resolution memory than do younger adults. From these data, we speculated that younger and older adults store the same number of items in VWM, but that younger adults store a higher-resolution representation than do older adults.
Asunto(s)
Envejecimiento/fisiología , Memoria a Corto Plazo/fisiología , Anciano , Análisis de Varianza , Electroencefalografía , Potenciales Evocados/fisiología , Femenino , Lateralidad Funcional/fisiología , Humanos , Masculino , Estimulación Luminosa , Desempeño Psicomotor/fisiología , Percepción Visual/fisiología , Adulto JovenRESUMEN
Over the past four decades, the characterization of memory loss associated with Alzheimer's disease (AD) has been extensively debated. Recent iterations have focused on disordered encoding versus rapid forgetting. To address this issue, we used a behavioral pattern separation task to assess the ability of the hippocampus to create and maintain distinct and orthogonalized visual memory representations in patients with amnestic mild cognitive impairment (aMCI) and mild AD. We specifically used a lag-based continuous recognition paradigm to determine whether patients with aMCI and mild AD fail to encode visual memory representations or whether these patients properly encode representations that are rapidly forgotten. Consistent with the rapid forgetting hypothesis of AD, we found that patients with aMCI demonstrated decreasing pattern separation rates as the lag of interfering objects increased. In contrast, patients with AD demonstrated consistently poor pattern separation rates across three increasingly longer lags. We propose a continuum that reflects underlying hippocampal neuropathology whereby patients with aMCI are able to properly encode information into memory but rapidly lose these memory representations, and patients with AD, who have extensive hippocampal and parahippocampal damage, cannot properly encode information in distinct, orthogonal representations. Our results also revealed that whereas patients with aMCI demonstrated similar behavioral pattern completion rates to healthy older adults, patients with AD showed lower pattern completion rates when we corrected for response bias. Finally, these behavioral pattern separation and pattern completion results are discussed in terms of the dual process model of recognition memory.
Asunto(s)
Enfermedad de Alzheimer/complicaciones , Disfunción Cognitiva/complicaciones , Trastornos de la Memoria/etiología , Reconocimiento Visual de Modelos/fisiología , Percepción Espacial/fisiología , Anciano , Anciano de 80 o más Años , Análisis de Varianza , Área Bajo la Curva , Aprendizaje por Asociación/fisiología , Sesgo , Femenino , Humanos , Masculino , Persona de Mediana Edad , Pruebas Neuropsicológicas , Estimulación Luminosa , Curva ROC , Factores de TiempoRESUMEN
The influence of implicit memory representations on explicit recognition may help to explain cases of accurate recognition decisions made with high uncertainty. During a recognition task, implicit memory may enhance the fluency of a test item, biasing decision processes to endorse it as "old". This model may help explain recognition-without-identification, a remarkable phenomenon in which participants make highly accurate recognition decisions despite the inability to identify the test item. The current study investigated whether recognition-without-identification for pictures elicits a similar pattern of neural activity as other types of accurate recognition decisions made with uncertainty. Further, this study also examined whether recognition-without-identification for pictures could be attained by the use of perceptual and conceptual information from memory. To accomplish this, participants studied pictures and then performed a recognition task under difficult viewing conditions while event-related potentials (ERPs) were recorded. Behavioral results showed that recognition was highly accurate even when test items could not be identified, demonstrating recognition-without-identification. The behavioral performance also indicated that recognition-without-identification was mediated by both perceptual and conceptual information, independently of one another. The ERP results showed dramatically different memory related activity during the early 300 to 500ms epoch for identified items that were studied compared to unidentified items that were studied. Similar to previous work highlighting accurate recognition without retrieval awareness, test items that were not identified, but correctly endorsed as "old," elicited a negative posterior old/new effect (i.e., N300). In contrast, test items that were identified and correctly endorsed as "old," elicited the classic positive frontal old/new effect (i.e., FN400). Importantly, both of these effects were elicited under conditions when participants used perceptual information to make recognition decisions. Conceptual information elicited very different ERPs than perceptual information, showing that the informational wealth of pictures can evoke multiple routes to recognition even without awareness of memory retrieval. These results are discussed within the context of current theories regarding the N300 and the FN400.
Asunto(s)
Concienciación/fisiología , Memoria/fisiología , Reconocimiento en Psicología/fisiología , Análisis de Varianza , Mapeo Encefálico , Electroencefalografía , Fenómenos Electrofisiológicos , Potenciales Evocados/fisiología , Femenino , Humanos , Masculino , Estimulación Luminosa , Desempeño Psicomotor/fisiología , Percepción Visual/fisiología , Adulto JovenRESUMEN
The purpose of this study was to examine whether the process of updating information in visual short-term memory (VSTM) is object based. We investigated whether modifying the memory of one feature of an object would automatically promote refreshing the memory of all of its other features. The results showed that the facilitative effect of updating was specific to the updated feature of an object and did not spread to its nonupdated features. This feature-selective effect suggests that updating VSTM is not object based (Experiment 1), even though storage was object based (Experiment 2). Control experiments ruled out strategy-based (Experiment 3) and stimulus-related (Experiments 4-6) accounts. Feature-selective updating may indicate that the mechanism used to modify the contents of memory may have a different basis than that used to encode or store information in memory.
Asunto(s)
Atención , Percepción de Color , Memoria a Corto Plazo , Orientación , Reconocimiento Visual de Modelos , Adolescente , Adulto , Discriminación en Psicología , Femenino , Humanos , Masculino , Psicofísica , Adulto JovenRESUMEN
Although most cases of acquired prosopagnosia are accompanied by bilateral brain lesions, a number also arise following right unilateral lesions. The prevailing consensus is that right hemisphere damage disrupts the configural apprehension of faces, which in turn forces a reliance on part-based processing. Here we describe a patient who following right hemisphere damage is not only unable to apprehend the configural aspects of faces, but is also unable to apprehend their component parts when these are presented within a whole, upright face. Intriguingly, the patient is able to apprehend face parts when these are presented in isolation, within inverted faces, or in unfamiliar, scrambled arrangements. Furthermore, the patient can make use of configural information to detect local changes in non-face stimuli. The findings uncover a hitherto unreported form of impairment following right unilateral damage, and raise questions about the role of the left hemisphere in processing local information.
Asunto(s)
Lesiones Encefálicas/complicaciones , Trastornos del Conocimiento/etiología , Cara , Lateralidad Funcional/fisiología , Reconocimiento Visual de Modelos/fisiología , Anciano , Análisis de Varianza , Lesiones Encefálicas/patología , Corteza Cerebral/fisiopatología , Humanos , Imagen por Resonancia Magnética , Masculino , Orientación/fisiología , Estimulación Luminosa/métodos , Tiempo de Reacción/fisiologíaRESUMEN
Patients with hemi-spatial neglect have trouble finding targets defined by a conjunction of visual features. The problem is widely believed to stem from a high-level deficit in attentional deployment, which in turn has led to disagreement over whether the detection of basic features is also disrupted. If one assumes that the detection of salient visual features can be based on the output of spared 'preattentive' processes (Treisman and Gelade, 1980), then feature detection should remain intact. However, if one assumes that all forms of detection require at least a modicum of focused attention (Duncan and Humphreys, 1992), then all forms of search will be disrupted to some degree. Here we measured the detection of feature targets that were defined by either a unique color or orientation. Comparable detection rates were observed in non-neglected space, which indicated that both forms of search placed similar demands on attention. For either of the above accounts to be true, the two targets should therefore be detected with equal efficiency in the neglected field. We found that while the detection rate for color was normal in four of our five patients, all showed an increased reaction time and/or error rate for orientation. This result points to a selective deficit in orientation discrimination, and implies that neglect disrupts specific feature representations. That is, the effects of neglect on visual search are not only attentional but also perceptual.
Asunto(s)
Atención , Percepción de Color , Orientación , Trastornos de la Percepción/diagnóstico , Percepción Espacial , Anciano , Discriminación en Psicología , Femenino , Humanos , Masculino , Persona de Mediana Edad , Trastornos de la Percepción/fisiopatología , Estimulación Luminosa , Tiempo de Reacción , Reconocimiento en Psicología , Campos VisualesRESUMEN
Researchers examining selective attentional mechanisms in patients with Alzheimer's disease (AD) often report impairment in patients' ability to inhibit irrelevant or distracting information. However, in many studies reporting such failures, researchers used tasks that require semantic processing, which a large body of literature documents to be disrupted in AD. The authors of this study used a spatial location-priming task that minimized semantic processing to examine the phenomena of negative priming and facilitative priming in 13 AD patients and 13 healthy older adults. AD patients demonstrated facilitative and negative priming proportionately equivalent to that of older adults. These findings suggest that both the facilitative and inhibitory mechanisms involved in selective attention are preserved in patients with AD and can be revealed in tasks that minimize semantic processing.
Asunto(s)
Enfermedad de Alzheimer/fisiopatología , Atención/fisiología , Inhibición Psicológica , Recuerdo Mental/fisiología , Percepción Espacial/fisiología , Anciano , Anciano de 80 o más Años , Análisis de Varianza , Femenino , Humanos , Masculino , Modelos Psicológicos , Pruebas Neuropsicológicas/estadística & datos numéricos , Tiempo de Reacción/fisiología , SemánticaRESUMEN
The remediative effect of galvanic vestibular stimulation (GVS) was investigated in a patient who, following right hemisphere damage, is profoundly unable to recognize faces. We administered a two-alternative forced choice match-to-sample task in which the patient had to choose which of two faces matched a sample face presented directly above, while bipolar, transcutaneous current was applied to the left and right vestibular nerves at a level below the patient's sensory threshold. Performance improved beyond the chance-level observed prestimulation, and relied on reversing the electrode polarity across two separate blocks of trials, such that each mastoid received positive current for one block and then negative charge for the next. Although our study involved only a single case, the data provide preliminary evidence that a deficit in perceptual face matching can be reduced by GVS. This raises the intriguing possibility that other unilateral visual disorders may also respond in such a manner.