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PubMed2006

Crossmodal change blindness between vision and touch.

Change blindness is the name given to people's inability to detect changes introduced between two consecutively-presented scenes when they are separated by a distractor that masks the transients that are typically associated with change. Change blindness has been reported within vision, audition, and touch, but has never before been investigated when successive patterns are presented to different sensory modalities. In the study reported here, we investigated change detection performance when the two to-be-compared stimulus patterns were presented in the same sensory modality (i.e., both visual or both tactile) and when one stimulus pattern was tactile while the other was presented visually or vice versa. The two to-be-compared patterns were presented consecutively, separated by an empty interval, or else separated by a masked interval. In the latter case, the masked interval could either be tactile or visual. The first experiment investigated visual-tactile and tactile-visual change detection performance. The results showed that in the absence of masking, participants detected changes in position accurately, despite the fact that the two to-be-compared displays were presented in different sensory modalities. Furthermore, when a mask was presented between the two to-be-compared displays, crossmodal change blindness was elicited no matter whether the mask was visual or tactile. The results of two further experiments showed that performance was better overall in the unimodal (visual or tactile) conditions than in the crossmodal conditions. These results suggest that certain of the processes underlying change blindness are multisensory in nature. We discuss these findings in relation to recent claims regarding the crossmodal nature of spatial attention.

Adult↗

PubMed2005

What aspects of vision facilitate haptic processing?

We investigate how vision affects haptic performance when task-relevant visual cues are reduced or excluded. The task was to remember the spatial location of six landmarks that were explored by touch in a tactile map. Here, we use specially designed spectacles that simulate residual peripheral vision, tunnel vision, diffuse light perception, and total blindness. Results for target locations differed, suggesting additional effects from adjacent touch cues. These are discussed. Touch with full vision was most accurate, as expected. Peripheral and tunnel vision, which reduce visuo-spatial cues, differed in error pattern. Both were less accurate than full vision, and significantly more accurate than touch with diffuse light perception, and touch alone. The important finding was that touch with diffuse light perception, which excludes spatial cues, did not differ from touch without vision in performance accuracy, nor in location error pattern. The contrast between spatially relevant versus spatially irrelevant vision provides new, rather decisive, evidence against the hypothesis that vision affects haptic processing even if it does not add task-relevant information. The results support optimal integration theories, and suggest that spatial and non-spatial aspects of vision need explicit distinction in bimodal studies and theories of spatial integration.

Adult↗

PubMed2006

Generalized multidimensional scaling: a framework for isometry-invariant partial surface matching.

An efficient algorithm for isometry-invariant matching of surfaces is presented. The key idea is computing the minimum-distortion mapping between two surfaces. For this purpose, we introduce the generalized multidimensional scaling, a computationally efficient continuous optimization algorithm for finding the least distortion embedding of one surface into another. The generalized multidimensional scaling algorithm allows for both full and partial surface matching. As an example, it is applied to the problem of expression-invariant three-dimensional face recognition.

Algorithms↗

PubMed2005

Voice recognition and cross-modal responses to familiar speakers' voices in prosopagnosia.

Recognizing the voices of people we know does not only activate "voice areas" in the temporal lobe but also extraauditory areas including the fusiform "face area" (FFA). This cross-modal effect could reflect that individual face and voice information become specifically associated when becoming acquainted with a person. Here, we addressed whether the ability to have individual face representations 1) plays a role in voice recognition and 2) is required to observe cross-modal responses to voices in face areas. We compared speaker recognition performance and neuroimaging responses during the processing of familiar and nonfamiliar speakers' voices in a developmental prosopagnosic subject (SO) with the respective findings obtained in a group of 9 control subjects. Despite scoring worse than controls on recognition of familiar speakers' voices, SO had normal cross-modal responses in the FFA and normal connectivity between FFA and the voice regions. However, she had reduced activations in areas that usually respond to familiarity with people. An indication for the malfunctioning of her FFA was reduced connectivity of the FFA to a subset of these supramodal areas. In combination these data suggest that 1) voice recognition benefits from the ability to process faces at an individual level and 2) cross-modal association of voices and faces in the brain is achieved by a sensory binding and does not depend on a top-down mechanism subsequent to successful person recognition.

Acoustic Stimulation↗

PubMed2006

Multisensory activation of the intraparietal area when classifying grating orientation: a functional magnetic resonance imaging study.

Humans can judge grating orientation by touch. Previous studies indicate that the extrastriate cortex is involved in tactile orientation judgments, suggesting that this area is related to visual imagery. However, it has been unclear which neural mechanisms are crucial for the tactile processing of orientation, because visual imagery is not always required for tactile spatial tasks. We expect that such neural mechanisms involve multisensory areas, because our perception of space is highly integrated across modalities. The current study uses functional magnetic resonance imaging during the classification of grating orientations to evaluate the neural substrates responsible for the multisensory spatial processing of orientation. We hypothesized that a region within the intraparietal sulcus (IPS) would be engaged in orientation processing, regardless of the sensory modality. Sixteen human subjects classified the orientations of passively touched gratings and performed two control tasks with both the right and left hands. Tactile orientation classification activated regions around the right postcentral sulcus and IPS, regardless of the hand used, when contrasted with roughness classification of the same stimuli. Right-lateralized activation was confirmed in these regions by evaluating the hemispheric effects of tactile spatial processing with both hands. In contrast, visual orientation classification activated the left middle occipital gyrus when contrasted with color classification of the same stimuli. Furthermore, visual orientation classification activated a part of the right IPS that was also activated by the tactile orientation task. Thus, we suggest that a part of the right IPS is engaged in the multisensory spatial processing of grating orientation.

Adult↗

PubMed2004

The neural mechanisms for minimizing cross-modal distraction.

The neural circuitry that increases attention to goal-relevant stimuli when we are in danger of becoming distracted is a matter of active debate. To address several long-standing controversies, we asked participants to identify a letter presented either visually or auditorily while we varied the amount of cross-modal distraction from an irrelevant letter in the opposite modality. Functional magnetic resonance imaging revealed three novel results. First, activity in sensory cortices that processed the relevant letter increased as the irrelevant letter became more distracting, consistent with a selective increase of attention to the relevant letter. In line with this view, an across-subjects correlation indicated that the larger the increase of activity in sensory cortices that processed the relevant letter, the less behavioral interference there was from the irrelevant letter. Second, regions of the dorsolateral prefrontal cortex (DLPFC) involved in orienting attention to the relevant letter also participated in increasing attention to the relevant letter when conflicting stimuli were present. Third, we observed a novel pattern of regional specialization within the cognitive division of the anterior cingulate cortex (ACC) for focusing attention on the relevant letter (dorsal ACC) versus detecting conflict from the irrelevant letter (rostral ACC). These findings indicate novel roles for sensory cortices, the DLPFC, and the ACC in increasing attention to goal-relevant stimulus representations when distracting stimuli conflict with behavioral objectives. Furthermore, they potentially resolve a long-standing controversy regarding the key contribution of the ACC to cognitive control.

Acoustic Stimulation↗

PubMedDate not supplied

[Working memory dysfunction in patients suffering from schizophrenia and their first-degree relatives].

UNLABELLED: Working memory deficits are considered to play an important role affecting not only the pathogenesis but also the course of schizophrenia. Numerous studies of schizophrenic patients and their first-degree relatives suggest that this impairment may be an indicator of susceptibility to developing schizophrenia. AIM: A comparison of selected working memory indicators in patients with schizophrenia, their first-degree relatives, and healthy controls. METHOD: Participants in the study were 99 patients with the diagnosis of schizophrenia (according to the ICD- 10-DCR criteria) in an early period of remission, their healthy first-degree relatives (N = 42), relatives with a history of psychiatric disorder (N = 14), and a control group of participants (N = 54) unrelated to the subjects and with no psychiatric history. Selected tests from the computer-aided Vienna Test Battery were used, measuring: reaction time (RT) in a task that required choosing among complex stimuli of two modalities, a tendency to perseveration (PERSEV), and immediate visuospatial memory span (CORSI). RESULTS: Schizophrenic patients' performance was found to be significantly inferior to that of controls on all the cognitive tests related to working memory: they had a longer reaction time in forced choice tasks, elevated perseverative tendencies and reduced immediate visuospatial memory span. Moreover, healthy relatives of schizophrenic patients performed significantly poorer than did the controls both as regards perseverative tendencies and visuospatial memory scan. Schizophrenic patients did not differ significantly from their close relatives in the degree of visuospatial memory span impairment. CONCLUSIONS: The findings indicate that working memory deficits as assessed by the tests used in the study may be related to familial susceptibility to schizophrenia. Therefore, the dysfunction may be taken into account in the capacity of endophenotype of such susceptibility.

Adult↗

PubMedDate not supplied

[Attention impairment in patients suffering from schizophrenia and their relatives of first-degree].

UNLABELLED: Attention dysfunction as assessed by standardised tests has often been reported in schizophrenic patients. Since many cognitive dysfunctions noted in these patients occur also in their close relatives, a supposition arises that they may be indicators not so much of transient states, but rather of a stable feature of cognitive functioning. This feature perhaps is transmitted from generation to generation and might contribute to the onset of the disease. AIM: A comparison of selected attention indicators in schizophrenic patients and their first-degree relatives with these in healthy controls without family history of schizophrenia. METHOD: Participants in the study were 99 patients diagnosed with schizophrenia (according to the ICD-10-DCR criteria) in an early period of remission, their first-degree relatives (N = 56), out of whom 42 were healthy and 14 had a history of psychiatric disorders, and a control group of participants (N = 42) unrelated to the subjects and with no psychiatric history. Several tests of the computer-aided Vienna Test Battery were used, and namely: the RT test measuring reaction time to simple visual or auditory stimuli, and LVT test measuring the accuracy and performance time in a task that consisted in visual tracking of lines, and required concentration of visual perception. RESULTS: As compared to the controls, the patient group was found to manifest attention deficits in the form of longer reaction time to simple stimuli as well as increased performance time and decreased correctness of visual line tracking. The patients had also a somewhat longer reaction time to visual (but not auditory) stimuli, and their line tracking was inferior as compared to that of their healthy relatives. As regards the reaction time to simple stimuli, the latter did not differ significantly from the controls, but in the line tracking test which required more attention, their performance was significantly inferior to that of the control group.

Adult↗

PubMed2001

Online pattern recognition in intensive care medicine.

In intensive care physiological variables of the critical-ly ill are measured and recorded in short time intervals. The existing alarm systems based on fixed thresholds produce a large number of false alarms. Usually the change of a variable over time is more informative than one pathological value at a particular time point. Intelligent alarm systems which detect important changes within a physiological time series are needed for suitable bedside decision support. There are various approaches to modeling time-dependent data and also several methodologies for pattern detection in time series. We compare several methodologies de-signed for online detection of measurement artifacts, level changes, and trends for a proper classification of the patient s state by means of a comparative case-study.

Aged↗

PubMed1988