PubMed Health⌕ Search

Biomedical subjects

Ken Nakayama

Publications and source records attributed to Ken Nakayama.

At least 19 recordsLinked to original sources
PubMed2006

Fixation offset facilitates saccades and manual reaching for single but not multiple target displays.

Turning off a fixation point, typically for 200 ms, before the onset of a peripheral target substantially reduces saccadic reaction times. This facilitatory effect generated by an inserted temporal gap between fixation offset and the target appearance is called the "gap" effect [J Opt Soc Am 57:1030-1033, 1967]. We show that the gap reduces the initial latency of both saccades and manual pointing in single and multiple target displays. Yet, in multiple target displays, the gap increased the movement duration because eye or hand movements were frequently misdirected toward distractors so that the trajectory had to be corrected. Thus, in spite of the shortened latency, the total time for trial completion was not shortened in multiple target displays, whereas it was reduced in single target displays. This selective gap effect for a single target was not restricted to goal-directed motor tasks because perceptual discrimination tasks, where no motor response is required, also demonstrated the gap effect only for single target displays. Our results suggest that the gap may facilitate attentional disengagement, but it does not help target selection in motor and perceptual discrimination tasks, where the allocation of attention to the target is required.

Adult↗
PubMed2006

Successful storage of peripheral nerves using University of Wisconsin solution with polyphenol.

We have previously reported that green tea polyphenol can preserve peripheral nerve segments for up to 1 month. In this study, we investigated the effect on peripheral nerve preservation of adding polyphenol to the conventional University of Wisconsin solution (UW solution), which has been widely used for organ storage. Twenty millimeter-long sciatic nerve segments, harvested from Lewis rats, were immersed in UW solution containing polyphenol (1 mg/mL) for 1 week and then in UW solution alone at 4 degrees C for 3 additional weeks before transplantation into recipient Lewis rats. Neural cell viability of the preserved nerve segments was confirmed by vital staining (calcein-AM/ethidium homodimer), electron microscopy, and genomic studies. Morphologically, nerve regeneration was similar to that of fresh isografts and superior to that of grafts stored with UW solution alone. Moreover, the electrophysiological results were equal to those of fresh isografts. Polyphenol has the potential to be used for peripheral nerve storage and could be useful for routine peripheral nerve banking.

Actins↗
PubMed2006

Role of focal attention on latencies and trajectories of visually guided manual pointing.

Previous studies have shown that an odd-colored target among uniformly colored distractors can be rapidly detected and localized using broadly distributed attention over an entire display. In the current study, we show that such a broadly distributed attentional allocation is not sufficient for seemingly effortless goal-directed manual pointing. Latencies and movement durations of manual pointing in odd-colored search tasks become shorter and curved trajectories decreased as the number of distractors increase or target color repetitions increases. Because these manipulations have been shown to facilitate the deployment of narrowly focused attention to a target but not for distributed attention, this adds further support to the view that focal attention is necessary for goal-directed action. In addition, the presence of highly curved movement trajectories, directed first to a distractor then to the target reflects ongoing changes in focal attentional deployment and target selection.

Attention↗
PubMed2006

Adaptation aftereffects in the perception of gender from biological motion.

Human visual perception is highly adaptive. While this has been known and studied for a long time in domains such as color vision, motion perception, or the processing of spatial frequency, a number of more recent studies have shown that adaptation and adaptation aftereffects also occur in high-level visual domains like shape perception and face recognition. Here, we present data that demonstrate a pronounced aftereffect in response to adaptation to the perceived gender of biological motion point-light walkers. A walker that is perceived to be ambiguous in gender under neutral adaptation appears to be male after adaptation with an exaggerated female walker and female after adaptation with an exaggerated male walker. We discuss this adaptation aftereffect as a tool to characterize and probe the mechanisms underlying biological motion perception.

Adaptation, Physiological↗
PubMed2006

Basic fibroblast growth factor promotes nerve regeneration in a C- -ion-implanted silicon chamber.

We reported previously that a silicone tube whose inner surface has been implanted with negatively charged carbon ions (C-) enables a nerve to regenerate across a 15-mm inter-stump gap. In this study, we investigated whether a C- -ion-implanted tube pretreated with basic fibroblast growth factor promotes peripheral nerve regeneration. The C- -ion-implanted tube significantly accelerated nerve regeneration, and this effect was enhanced by basic fibroblast growth factor.

Action Potentials↗
PubMed2006

Developmental prosopagnosia: a window to content-specific face processing.

Developmental prosopagnosia is characterized by severely impaired face recognition. Individuals with this disorder, which often runs in families, have no history of brain damage and intact early visual processing systems. Recent research has also demonstrated that many developmental prosopagnosics have normal or relatively good object recognition, indicating that their impairments are not the result of deficits to a unitary visual recognition mechanism. To investigate the nature of the impaired mechanisms, extensive testing was done on an individual with especially pure face processing deficits. The results ruled out all extant explanations of prosopagnosia except one that proposed that faces are recognized by a content-specific face processing mechanism. fMRI and MEG studies show that there are a variety of neural profiles in developmental prosopagnosia, which is consistent with behavioral studies demonstrating that it is a heterogeneous disorder.

Brain↗
PubMed2006

Rapid face-selective adaptation of an early extrastriate component in MEG.

Adaptation paradigms are becoming increasingly popular for characterizing visual areas in neuroimaging, but the relation of these results to perception is unclear. Neurophysiological studies have generally reported effects of stimulus repetition starting at 250-300 ms after stimulus onset, well beyond the latencies of components associated with perception (100-200 ms). Here we demonstrate adaptation for earlier evoked components when 2 stimuli (S1 and S2) are presented in close succession. Using magnetoencephalography, we examined the M170, a "face-selective" response at 170 ms after stimulus onset that shows a larger response to faces than to other stimuli. Adaptation of the M170 occurred only when stimuli were presented with relatively short stimulus onset asynchronies (< 800 ms) and was larger for faces preceded by faces than by houses. This face-selective adaptation is not merely low-level habituation to physical stimulus attributes, as photographic, line-drawing, and 2-tone face images produced similar levels of adaptation. Nor does it depend on the amplitude of the S1 response: adaptation remained greater for faces than houses even when the amplitude of the S1 face response was reduced by visual noise. These results indicate that rapid adaptation of early, short-latency responses not only exists but also can be category selective.

Adaptation, Physiological↗
PubMed2006

Priming race in biracial observers affects visual search for Black and White faces.

We examined whether or not priming racial identity would influence Black-White biracial individuals' ability to visually search for White and Black faces. Black, White, and biracial participants performed a visual search task in which the targets were Black or White faces. Before the task, the biracial participants were primed with either their Black or their White racial identity. All participant groups detected Black faces faster than White faces. Critically, the results also showed a racial-prime effect in biracial individuals: The magnitude of the search asymmetry was significantly different for those primed with their White identity and those primed with their Black identity. These findings suggest that top-down factors such as one's racial identity can influence mechanisms underlying the visual search for faces of different races.

Adult↗
PubMed2005

Orientation tuning of human face processing estimated by contrast matching in transparency displays.

Upright images of faces appear more salient than faces of other orientations. We exploited this effect in a titration experiment where faces were superimposed in transparency. By manipulating the physical contrast of the component images, we measured the degree of perceptual dominance as function of the orientation of the face in the image plane. From these measurements, we obtain the orientation tuning of face processing, which is well approximated by a Gaussian function with a SD of about 45 deg and mean centered on upright. Faces predominantly lit from above and from below produced very similar results. However, when presented with scrambled faces observers showed no orientation preference. We argue that these results can be explained by the existence of specialized face processing mechanisms with an orientation tuning with a bandwidth of approximately 90 deg, predominantly centered on the upright orientation and easily disrupted by alterations of the normal facial configuration.

Contrast Sensitivity↗
PubMed2005

The Cambridge Face Memory Test: results for neurologically intact individuals and an investigation of its validity using inverted face stimuli and prosopagnosic participants.

The two standardized tests of face recognition that are widely used suffer from serious shortcomings [Duchaine, B. & Weidenfeld, A. (2003). An evaluation of two commonly used tests of unfamiliar face recognition. Neuropsychologia, 41, 713-720; Duchaine, B. & Nakayama, K. (2004). Developmental prosopagnosia and the Benton Facial Recognition Test. Neurology, 62, 1219-1220]. Images in the Warrington Recognition Memory for Faces test include substantial non-facial information, and the simultaneous presentation of faces in the Benton Facial Recognition Test allows feature matching. Here, we present results from a new test, the Cambridge Face Memory Test, which builds on the strengths of the previous tests. In the test, participants are introduced to six target faces, and then they are tested with forced choice items consisting of three faces, one of which is a target. For each target face, three test items contain views identical to those studied in the introduction, five present novel views, and four present novel views with noise. There are a total of 72 items, and 50 controls averaged 58. To determine whether the test requires the special mechanisms used to recognize upright faces, we conducted two experiments. We predicted that controls would perform much more poorly when the face images are inverted, and as predicted, inverted performance was much worse with a mean of 42. Next we assessed whether eight prosopagnosics would perform poorly on the upright version. The prosopagnosic mean was 37, and six prosopagnosics scored outside the normal range. In contrast, the Warrington test and the Benton test failed to classify a majority of the prosopagnosics as impaired. These results indicate that the new test effectively assesses face recognition across a wide range of abilities.

Adolescent↗
PubMed2005

Resolving border disputes in midlevel vision.

Two papers in this issue of Neuron specify the coding of border ownership, the basis of figure-ground segmentation, in early extrastriate visual cortex (area V2). Recording from a population of neurons, Qiu and von der Heydt show that border ownership assignments based on 2D images show the same bias when tested with stereopsis. Zhaoping shows that a neural model of V2 can make appropriate border assignments based on 2D images.

Form Perception↗
PubMed2005

Normal and abnormal face selectivity of the M170 response in developmental prosopagnosics.

Developmental prosopagnosia is a lifelong impairment in face recognition despite normal low-level visual processing. Here we used magnetoencephalography (MEG) to examine the M170 response, a component occurring approximately 170 ms after stimulus onset, in a group of five developmental prosopagnosics. In normal subjects, the M170 is "face-selective", with a consistently higher amplitude to faces than to a wide variety of other visual stimulus categories; the N170, a component recorded using event-related potentials (ERP) and thought to be analogous to the M170, also shows this "face selectivity". Two previous ERP studies with developmental prosopagnosics have found attenuation or absence of face selectivity in the N170 response of these subjects [Bentin, S., Deouell, L. Y., and Soroker, N. (1999). Selective visual streaming in face recognition: Evidence from developmental prosopagnosia. Neuroreport, 10, 823-827; Kress, T., and Daum, I. (2003). Event-related potentials reflect impaired face recognition in patients with congenital prosopagnosia. Neuroscience Letters, 352, 133-136]. Three of our developmental prosopagnosic group showed this non-selective pattern at the M170 while the remaining two prosopagnosics were indistinguishable from normal controls. Thus, impaired face recognition is not necessarily correlated with an absence of the "face-selective" M170. Furthermore, ERP recordings collected simultaneously in the two developmental prosopagnosics with seemingly selective M170s also showed N170s within the same normal selective range, demonstrating that the face-selective signals found with MEG are not due to differences between MEG and ERP. While the presence of face selectivity at these neurophysiological markers is insufficient for predicting normal behavioral performance with faces, it could help to distinguish different classes of face recognition deficits.

Adult↗
PubMed2005

Dissociations of face and object recognition in developmental prosopagnosia.

Neuropsychological studies with patients suffering from prosopagnosia have provided the main evidence for the hypothesis that the recognition of faces and objects rely on distinct mechanisms. Yet doubts remain, and it has been argued that no case demonstrating an unequivocal dissociation between face and object recognition exists due in part to the lack of appropriate response time measurements (Gauthier et al., 1999). We tested seven developmental prosopagnosics to measure their accuracy and reaction times with multiple tests of face recognition and compared this with a larger battery of object recognition tests. For our systematic comparison, we used an old/new recognition memory paradigm involving memory tests for cars, tools, guns, horses, natural scenes, and houses in addition to two separate tests for faces. Developmental prosopagnosic subjects performed very poorly with the face memory tests as expected. Four of the seven prosopagnosics showed a very strong dissociation between the face and object tests. Systematic comparison of reaction time measurements for all tests indicates that the dissociations cannot be accounted for by differences in reaction times. Contrary to an account based on speed accuracy tradeoffs, prosopagnosics were systematically faster in nonface tests than in face tests. Thus, our findings demonstrate that face and nonface recognition can dissociate over a wide range of testing conditions. This is further support for the hypothesis that face and nonface recognition relies on separate mechanisms and that developmental prosopagnosia constitutes a disorder separate from developmental agnosia.

Adult↗
PubMed2005

Efficient visual search without top-down or bottom-up guidance.

Two types of mechanisms have dominated theoretical accounts of efficient visual search. The first are bottom-up processes related to the characteristics of retinotopic feature maps. The second are top-down mechanisms related to feature selection. To expose the potential involvement of other mechanisms, we introduce a new search paradigm whereby a target is defined only in a context-dependent manner by multiple conjunctions of feature dimensions. Because targets in a multiconjunction task cannot be distinguished from distractors either by bottom-up guidance or top-down guidance, current theories of visual search predict inefficient search. While inefficient search does occur for the multiple conjunctions of orientation with color or luminance, we find efficient search for multiple conjunctions of luminance/size, luminance/shape, and luminance/topology. We also show that repeated presentations of either targets or a set of distractors result in much faster performance and that bottom-up feature extraction and top-down selection cannot account for efficient search on their own. In light of this, we discuss the possible role of perceptual organization in visual search. Furthermore, multiconjunction search could provide a new method for investigating perceptual grouping in visual search.

Form Perception↗
PubMed2004

Normal greeble learning in a severe case of developmental prosopagnosia.

A central question in cognitive neuroscience is whether mechanisms exist that are specialized for particular domains. One of the most commonly cited examples of a domain-specific competence is the human ability to recognize upright faces. However, according to a widely discussed alternative hypothesis, face recognition is instead performed by mechanisms specialized for processing any object class for which an individual has expertise. Faces, according to this domain-general hypothesis, are just one example of an expert class. Nonface object expertise has been intensively investigated using a training procedure involving an artificial stimulus class known as greebles. A key prediction of this hypothesis is that individuals with face recognition impairments will also have impairments with other categories that control subjects have expertise with. Our results show that a man with severe prosopagnosia performed normally throughout the standard greeble training procedure. These findings indicate that face recognition and greeble recognition rely on separate mechanisms.

Female↗
PubMed2004

Developmental prosopagnosia and the Benton Facial Recognition Test.

The Benton Facial Recognition Test is used for clinical and research purposes, but evidence suggests that it is possible to pass the test with impaired face discrimination abilities. The authors tested 11 patients with developmental prosopagnosia using this test, and a majority scored in the normal range. Consequently, scores in the normal range should be interpreted cautiously, and testing should always be supplemented by other face tests.

Discrimination, Psychological↗
PubMed2004

No disgust recognition deficit in obsessive-compulsive disorder.

BACKGROUND: Patients with basal ganglia abnormalities misclassify facial expressions of disgust as expressions of anger when asked to identify the emotion depicted in photographs of individuals displaying different emotions. Sprengelmeyer, Young, Pundt et al. (1997) reported a similar disgust recognition deficit in patients with obsessive-compulsive disorder (OCD)--an anxiety disorder associated with basal ganglia abnormality. METHODS: In the present experiment, we attempted to replicate Sprengelmeyer, Young, Pundt et al.'s (1997) findings. RESULTS: We failed to replicate Sprengelmeyer, Young, Pundt et al.'s finding of disgust recognition deficits in OCD patients relative to healthy control subjects. One patient with especially severe OCD did, however, exhibit impairment by misclassifying disgust expressions as anger expressions. DISCUSSION: These data do not confirm the presence of disgust recognition deficits in individuals with OCD. In light of the deficits exhibited by one subject with severe OCD, disgust recognition deficits may be confined to an unidentified subset of people with OCD.

Adult↗