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PubMed2005

Neural correlates of switching from auditory to speech perception.

Many people exposed to sinewave analogues of speech first report hearing them as electronic glissando and, later, when they switch into a 'speech mode', hearing them as syllables. This perceptual switch modifies their discrimination abilities, enhancing perception of differences that cross phonemic boundaries while diminishing perception of differences within phonemic categories. Using high-density evoked potentials and fMRI in a discrimination paradigm, we studied the changes in brain activity that are related to this change in perception. With ERPs, we observed that phonemic coding is faster than acoustic coding: The electrophysiological mismatch response (MMR) occurred earlier for a phonemic change than for an equivalent acoustic change. The MMR topography was also more asymmetric for a phonemic change than for an acoustic change. In fMRI, activations were also significantly asymmetric, favoring the left hemisphere in both perception modes. Furthermore, switching to the speech mode significantly enhanced activation in the posterior parts of the left superior gyrus and sulcus relative to the non-speech mode. When responses to a change of stimulus were studied, a cluster of voxels in the supramarginal gyrus was activated significantly more by a phonemic change than by an acoustic change. These results demonstrate that phoneme perception in adults relies on a specific and highly efficient left-hemispheric network, which can be activated in top-down fashion when processing ambiguous speech/non-speech stimuli.

Adult↗

PubMed2005

Depth perception by the active observer.

The connection between perception and action has classically been studied in one direction only: the effect of perception on subsequent action. Although our actions can modify our perceptions externally, by modifying the world or our view of it, it has recently become clear that even without this external feedback the preparation and execution of a variety of motor actions can have an effect on three-dimensional perceptual processes. Here, we review the ways in which an observer's motor actions--locomotion, head and eye movements, and object manipulation--affect his or her perception and representation of three-dimensional objects and space. Allowing observers to act can drastically change the way they perceive the third dimension, as well as how scientists view depth perception.

Depth Perception↗

PubMed2003

Multisensory contributions to the perception of motion.

The ability to process motion is crucial for coherent perception and action. While the majority of studies have focused on the unimodal factors that influence motion perception (see, for example, the other chapters in this Special Issue), some researchers have also investigated the extent to which information presented in one sensory modality can affect the perception of motion for stimuli presented in another modality. Although early studies often gave rise to mixed results, the development of increasingly sophisticated psychophysical paradigms are now enabling researchers to determine the spatiotemporal constraints on multisensory interactions in the perception of motion. Recent findings indicate that these interactions stand over-and-above the multisensory interactions documented previously for static stimuli, such as the oft-cited 'ventriloquism' effect. Neuroimaging and neuropsychological studies are also beginning to elucidate the network of neural structures responsible for the processing of motion information in the different sensory modalities, an important first step that will ultimately lead to the determination of the neural substrates underlying these multisensory contributions to motion perception.

Animals↗

PubMed2000

A transient deficit of motion perception in human.

We studied the motion perception abilities in a young adult, SF, who had her right occipito-temporal cortices resected to treat epilepsy. Following resection, SF showed transient deficits of both first- and second-order motion perception that recovered to normal within weeks. Previous human studies have shown either first- or second n order motion deficits that have lasted months or years after cerebral damage. SF also showed a transient defect in processing of shape-from-motion with normal perception of shape from non-motion cues. Furthermore, she showed greatly increased reaction times for a mental rotation task, but not for a lexical decision task. The nature and quick recovery of the deficits in SF resembles the transient motion perception deficit observed in monkey following ibotenic acid lesions, and provides additional evidence that humans possess specialized cortical areas subserving similar motion perception functions.

Adult↗

PubMed1999

Abnormal depth perception from motion parallax in amblyopic observers.

Many similarities exist between the perception of depth from binocular stereopsis and that from motion parallax. Moreover, Rogers (1984, cited in, Howard, I. P., & Rogers, B. J. (1995). Binocular vision and stereopsis. Oxford Claridon, New York.) suggests a relationship between an observer's ability to use disparity information and motion parallax information in a depth perception task. To more closely investigate this relationship, depth perception was studied in normal observers and amblyopic observers with poor stereo vision. As expected, amblyopic observers performed much worse than normal observers on depth discriminations requiring use of binocular disparity. However, amblyopic observers also performed much worse than normal observers on depth discriminations based on motion parallax. This result provides supporting evidence for a psychoanatomical link between the perception of depth from motion and the perception of depth from binocular disparity.

Amblyopia↗

PubMed2006

Lightness, filling-in, and the fundamental role of context in visual perception.

Visual perception is defined by the unique spatial interactions that distinguish it from the point-to-point precision of a photometer. Over several decades, Lothar Spillmann has made key observations about the nature of these interactions and the role of context in perception. Our lab has explored the perceptual properties of spatial interactions and more generally the importance of visual context for neuronal responses and perception. Our investigations into the spatiotemporal dynamics of lightness provide insight into underlying mechanisms. For example, backward masking and luminance modulation experiments suggest that the representation of a uniformly luminous object develops first at the borders and, in some manner, the center fills in. The temporal dynamics of lightness induction are also consistent with a filling-in process. There is a slow cutoff temporal frequency above which surround luminance modulation will not elicit perceptual induction of a central area. The larger the central area, the lower the cutoff frequency for induction, perhaps indicating that an edge-based process requires more time to "complete" the larger area. In recordings from primary visual cortex we find that neurons respond in a manner surprisingly consistent with lightness perception and the spatial and temporal properties of induction. For example, the activity of V1 neurons can be modulated by light outside the receptive field and as the modulation rate is increased response modulation falls off more rapidly for large uniform areas than smaller areas. The conclusion we draw from these experiments is that lightness appears to be computed slowly on the basis of edge and context information. A possible role for the spatial interactions is lightness constancy, which is thought to depend on extensive spatial integration. We find not only that V1 responses are strongly context dependent, but that this dependence makes V1 lightness constant on average. The dependence of constancy on surround interactions underscores the fundamental role that context plays in perception. In more recent studies, further support has been found for the importance of context in experiments using natural scene stimuli.

Animals↗

PubMed2003

Neural networks active during tactile form perception: common and differential activity during macrospatial and microspatial tasks.

Prior studies have shown that tactile perception recruits activity not only in somatosensory but also in visual cortical areas. The present study used functional magnetic resonance imaging to investigate the distribution of neural activity during tactile perception of 2D form. In a macrospatial form task, raised letters (uppercase T and V) were presented upside-down. In a microspatial form task, a bar, either with or without a gap, was presented. Stimuli were applied to the immobilized right index fingerpad. Six neurologically normal volunteers were studied in a block design paradigm, with alternating blocks of rest and covert discrimination between the two alternatives for a task. Each task was studied in a separate run. Contrasting macrospatial form discrimination against rest revealed activity in an extensive, bilateral network of cortical and subcortical regions, including areas of somatosensory cortex and the intraparietal sulcus (IPS), occipito-temporal cortex, dorsal and ventral premotor cortex, medial superior frontal cortex, lateral inferior frontal cortex, thalamus and cerebellar hemispheres. Contrasting (microspatial) gap detection against rest showed activity in a similar network, with the notable exception of the occipito-temporal cortical regions. A direct contrast between the two tasks yielded greater activity for the macrospatial than microspatial task in these occipito-temporal regions bilaterally, and also in foci near the right IPS and in the right cerebellar hemisphere. The occipito-temporal cortical activations were in the lateral occipital complex, a part of the ventral visual pathway active during visual form perception. Thus, macrospatial form perception preferentially recruits this region of extrastriate visual cortex, compared to microspatial form perception.

Adult↗

PubMed2004

Assessment of time perception: the effect of aging.

Studies concerning time perception lack a validated assessment tool and a consensual "gold-standard" measure. Moreover, the present evidence suggests modification of timing with aging. This study aimed to develop and validate a neuropsychological tool to measure time perception and to study temporal perception with aging. Eighty-six healthy participants, aged 15-90 years old, were asked to verbally estimate and produce empty intervals signaled by auditory beeps, of 7-, 32-, and 58-s duration. Two tests were used as "gold-standards": estimation of the duration of time necessary to draw a clock ("clock time") and estimation of the duration of neuropsychological evaluation ("global time"). Results showed a correlation between estimation and production (p < .01) and a correlation between estimation or production and "global time" (p < .01). The correlation between either estimation or production and age (p < .01), suggested a faster "internal-clock" in the older participants. However, this finding lost significance when controlled for literacy. The results suggest that these tests are potentially a useful tool to measure subjective perception of time. They also corroborate the hypothesis of a change in subjective time perception with aging. It was not possible to conclude if this effect was a specific result of aging or biased by the interference of literacy.

Adolescent↗

PubMed1983

Four assumptions about invariance in perception.

The term invariance has become more central to current views of perception. I take this as a good trend, but the term is rooted in mathematics, and its use in perception brings with it a host of assumptions that have generally been unexamined. The purpose of this article is to state some of these assumptions and assess their validity, with the hope that we can continue to find the term useful while acknowledging its limitations. The assumptions discussed are that (a) mathematics is an appropriate descriptive language for perception, (b) mathematical truths are transportable into perception without change of meaning, (c) mathematical imports are useful in explaining perception, and (d) perceptual invariants, like their mathematical counterparts, are absolute and not subject to threshold considerations.

Humans↗

PubMed2000

Distinct representations of eye gaze and identity in the distributed human neural system for face perception.

Face perception requires representation of invariant aspects that underlie identity recognition as well as representation of changeable aspects, such as eye gaze and expression, that facilitate social communication. Using functional magnetic resonance imaging (fMRI), we investigated the perception of face identity and eye gaze in the human brain. Perception of face identity was mediated more by regions in the inferior occipital and fusiform gyri, and perception of eye gaze was mediated more by regions in the superior temporal sulci. Eye-gaze perception also seemed to recruit the spatial cognition system in the intraparietal sulcus to encode the direction of another's gaze and to focus attention in that direction.

Adult↗

PubMed1998

Perception metamorphosis phenomenon in autism.

It is well known that various perceptual abnormalities exist in autism. However, because perceptual phenomena are intersubjective, a phenomenological approach is required for getting hold of the reality of the modes of perception involved in autism. From this standpoint, the author has proposed the concept of 'perception metamorphosis phenomenon' (PMP) as the mode of perception peculiar to autistics. This mode of perception is notable to some degree in infancy and adolescence, and points to the appearance of behavior that is indicative of the environmental world being perceived in a manner different from before by the autistic child. The phenomenon has been classified into three basic categories according to the aspect of perception: (i) visual PMP; (ii) auditory PMP; and (iii) situational PMP. The proposal of this concept was made with the objective of capturing the onset of autism or the mechanism of appearance of the various symptoms from a more phenomenological viewpoint, to serve as a possible starting point for understanding the inner world of autistics. The proposal was made emphasizing the validity of this approach in mapping out new therapeutic approaches and for re-investigating the relationship between autism and schizophrenia.

Adolescent↗

PubMed1998

[Visual perception of movement. A normative study].

BACKGROUND: A battery of tests has been developed to better define the variety of defects which can occur in the process of visual perception of motion. METHODS: The tests assessed the perception of 1) coherent motion, in each of the four cardinal directions; (2) form from motion; (3) flow in depth; and (4) motion of a target moving in depth, within or without an optic flow surround. A normative study was conducted with 34 subjects, 21 to 69 years of age. RESULTS: Recognition of form from motion was better with upwards than with downwards motion. Perception of motion in depth was better with backward than forwards motion. The presence of an optic flow altered the perception of a motion in depth. CONCLUSION: The recognition of form from motion demonstrated an asymmetry in threshold between the upward and downward movements. This asymmetry did not occur with global coherent motion, thus reflecting the variety of mechanisms involved in the visual process of motion. Moreover, alteration of perception of motion in depth within an optic flow reflected background effect.

Adult↗

PubMed2002

The effects of age on auditory speech perception development in cochlear-implanted prelingually deaf children.

One of the most important factors in auditory speech perception of cochlear-implanted children is age. The goal of this study was to compare auditory speech perception among children implanted from 6 different age groups: 0 to 3, 4 to 5, 6 to 7, 8 to 9, 10 to 11, and >12 years. The subjects of this study were matched based on socioeconomic status, residual hearing before cochlear implantation, the kinds of cochlear implant device, speech processing strategy, communication mode after implantation, and primary language in family. All of them have used the device minimally for 2 years. The subjects were tested with a range of closed and open-set auditory speech perception tests, and the levels of auditory speech perception in different age groups were compared. Results showed that the children who received an implant at 0 to 3 years of age had maximum auditory speech perception.

Adolescent↗

PubMed2003

The role of facial colour and luminance in visual and audiovisual speech perception.

We conducted four experiments to investigate the role of colour and luminance information in visual and audiovisual speech perception. In experiments 1a (stimuli presented in quiet conditions) and 1b (stimuli presented in auditory noise), face display types comprised naturalistic colour (NC), grey-scale (GS), and luminance inverted (LI) faces. In experiments 2a (quiet) and 2b (noise), face display types comprised NC, colour inverted (CI), LI, and colour and luminance inverted (CLI) faces. Six syllables and twenty-two words were used to produce auditory and visual speech stimuli. Auditory and visual signals were combined to produce congruent and incongruent audiovisual speech stimuli. Experiments 1a and 1b showed that perception of visual speech, and its influence on identifying the auditory components of congruent and incongruent audiovisual speech, was less for LI than for either NC or GS faces, which produced identical results. Experiments 2a and 2b showed that perception of visual speech, and influences on perception of incongruent auditory speech, was less for LI and CLI faces than for NC and CI faces (which produced identical patterns of performance). Our findings for NC and CI faces suggest that colour is not critical for perception of visual and audiovisual speech. The effect of luminance inversion on performance accuracy was relatively small (5%), which suggests that the luminance information preserved in LI faces is important for the processing of visual and audiovisual speech.

Acoustic Stimulation↗

PubMed1977

Microteaching, feedback, dogmatism, and nonverbal perceptiveness.

This exploratory study examines the relationship between various conditions of feedback in peer microteaching, the personality dimension dogmatism, and nonverbal perceptiveness. Ss were 74 trainee teachers who were assigned to feedback conditions on the basis of dogmatism scores and then participated in a seven-week treatment period. The statistical procedure known as part correlation was used to gain measures of the extent to which Ss changed their nonverbal perceptiveness. This measure of change in nonverbal perceptiveness was related to dogmatic tendencies and feedback conditions. Although no consistent relationship was found to exist between dogmatism and change in nonverbal perceptiveness, there was a strong indication of dogmatic Ss changing their nonverbal perceptiveness when involved in the treatment condition peer microteaching with public feedback.

Auditory Perception↗

PubMed2003

Speech perception after cochlear implantation over a 4-year time period.

OBJECTIVE: To evaluate the long-term speech perception of cochlear implantees and to compare the developing auditory performance patterns of prelingual children and postlingual deaf adults. MATERIAL AND METHODS: Twenty-nine prelingually deaf children and 17 postlingually deaf adults who had been followed up for 4 years were included in the study. Speech perception ability was assessed by means of vowel and consonant confusion tests and the Korean version of the Central Institute of Deafness (K-CID) test (performed without visual cues). The test results were analyzed at 3 and 6 months after implantation and then annually. RESULTS: In the prelingually deaf children, the average results continuously improved over the 4-year period. In the postlingually deaf adults, the average results did not improve further after the first 2 years. Individuals with < 5 years of deafness had a faster rate of recovery of speech perception than those who had been deaf for > 5 years. The K-CID scores were negatively correlated with age at implantation for the prelingually deaf group and with the duration of deafness in the postlingually deaf group. Children fitted with implants at a younger age showed better speech perception ability than those fitted with implants at an older age. Interestingly, prelingually deaf children aged 5-7 years at implantation showed the widest variation in individual outcomes. Amongst this group of children with highly variable outcomes, the metabolic status of brain cortices determined by means of 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) was available for three patients. The individual with the widest hypometabolic area had the best speech perception ability. CONCLUSION: The extent of hypometabolism as assessed by FDG-PET seemed to be one of the major factors predicting the outcome of cochlear implantation.

Adult↗

PubMed2001

Human perceptions of sports equipment under playing conditions.

Assessment of the 'performance' of sports equipment is generally derived from physical and technical parameters, such as power, speed, distance and accuracy. However, from a psychological perspective, players need to feel comfortable with their equipment and confident in its properties. These factors can only be measured through the subjective assessment of individual perceptions. Focusing on a group of elite golfers, this study presents a formalized approach for eliciting and structuring players' descriptions of their perception of sports equipment. Qualitative methods of inquiry were used to generate perceptions from a group of professional golfers (n = 15) during play testing. The equipment characteristics of significance to the golfers emerged from an inductive analysis of their responses. However, although this method of representation of the results helped to identify the key components or dimensions of a player's subjective perception, it was unable to determine potential relationships between the dimensions. With this in mind, a new technique, called 'structured relationship modelling', was developed. Ten general dimensions emerged from the analysis, of which three are presented here together with a section of the relationship model. The results demonstrate the effectiveness of qualitative techniques for eliciting human perceptions and of structured relationship models for representation of the associations found.

Adult↗

PubMed2004

Influence of motor disorders on the visual perception of human movements in a case of peripheral dysgraphia.

We report the case of a 71 year-old female patient (DC) with a left parietal lesion resulting in a peripheral dysgraphia essentially characterized by difficulties in letter sequences writing. The aim of our experiments was to analyze the influence of motor difficulties on the visual perception of both writing and reaching movements. Results showed a strong link between motor and perceptual performance. For reaching movements, performances in both production and perception tasks conform to the motor principles identified in healthy subjects (Fitts' law and motor anticipation). By contrast, for handwriting movements, DC's productions do not follow the motor principles usually observed in normal subjects (isochrony principle, motor anticipation) and in perception the same results were observed. The motor references used by DC in the visual perception of writing movement were not the laws of movement but rather her own way of writing. Taken together these data strongly suggest that motor competences is involved in the visual perception of human movements. They are discussed in the general framework of the simulation theory.

Aged↗