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Bugs in vision
News & Comment
TRENDS in Cognitive Sciences Vol.5 No.8 August 2001
331
In Brief
We’ve all got rhythm The timing of rhythmic actions, such as finger tapping, is sensitive to temporal differences below the level of conscious detection, according to new research [J. Exp. Psychol. Hum. Percept. Perform. (2001) 27, 600–621]. Bruno Repp and colleagues asked people to tap along to an auditory rhythm. Without telling his subjects, Repp occasionally altered the timing of the beat very slightly. These changes were so subtle that subjects did not consciously perceive any alteration in rhythm. However, they accurately updated their finger movements in response to the change. This suggests that the brain contains a timekeeper that can use subliminal timing information to control movement accurately. HJB
Bugs in odometry Desert ants can perform a remarkable feat of navigation – after travelling a complex path, they ‘know’ the exact direction and distance to their home base. In order to perform this navigational task, ants need to integrate both their rotation and translation, updating their position vector with respect to the nest. How ants measure linear distance travelled – their ‘odometer’ – has been unknown. However, Sandra Wohlgemuth and her colleagues [Nature (2001) 411, 795–798] have recently discovered that the odometer of the genus Cataglyphis is sophisticated enough to take the third dimension into account. When ants travel along a steep slope, they count distance along the ground, rather than the length of their path: when they return home on flat terrain, they compensate for ground distance, rather than for path length. Wohlgemuth et al. showed that this compensation for ups and downs does not use tricks based on energy expenditure, travel time, or optic flow, and therefore must be based on the perception of the ant’s angle with respect to the direction of gravity. Will they send ants into space to make sure? MW
Bugs in vision Most non-experts naively believe that what they see accurately reflects what they look at, much as a photographic image faithfully portrays a scene. Hence the interest of visual illusions, which, by exposing the subtle ‘bugs’ of vision, demonstrate the complexity of http://tics.trends.com
constructing a visual representation of the world. Recently, however, Yoram Bonneh and his co-workers [Nature (2001) 411, 798–801] have uncovered a most unsubtle and embarrassingly visible bug in vision: bright steady objects, superimposed over a moving field, seem to disappear for several seconds as one looks at them (demonstrations can be downloaded at http://www.weizmann.ac.il/ ~masagi/MIB/mib.html). This motioninduced blindness effect, which occurs under normal viewing conditions and for a variety of stimulus parameters, subjectively feels as though the disappearing objects suddenly entered the retinal blind spot. In recent years, a variety of ‘attentional blindness’ effects have shown that we can miss even quite important changes, unless we pay close attention. The originality of motioninduced blindness is that it results in actual disappearance of objects, even when we pay attention to them. MW
Neglecting the temporal lobe One of the first things today’s student of cognitive neuroscience learns is the ‘what and where’ doctrine: the temporal lobe processes information about form whereas the parietal lobe processes information about space. This doctrine is strengthened by centuries of documented cases of hemispatial visual neglect – a deficit in spatial awareness thought to occur after parietal lobe damage. However, these ideas are challenged by a recent study that analysed the locations of lesions in a group of patients who had neglect, with or without additional visual deficits [Nature (2001) 411, 950–953]. Detailed analysis revealed that pure neglect (without associated visual defects) was associated with damage to the superior temporal cortex; damage to the posterior parietal cortex was associated only with visual field blindness. This finding could reconcile the discrepancy between the human data and the animal literature where neglect is only observed after damage to the superior temporal cortex. HJB
who will receive the award in August in Edinburgh, at the Annual Meeting of the Cognitive Science Society (www.hcrc.ed.ac.uk/cogsci2001). He will deliver the Prize Lecture, on designing generative models, at the meeting. Hinton is currently Director of the Gatsby Computational Neuroscience Unit at UCL and is an obvious choice for the award, having made several groundbreaking contributions to the analysis of representation, processing and learning in neural networks. The prize (www.cnbc.cmu.edu/derprize) will now be awarded annually, instead of biennially, because of the significant number of outstanding candidates, and the second recipient will be announced at the Edinburgh meeting. DPB
Tactile motion activates V5 Current thinking on the type of inputs that drive ‘visual’ areas might need to be reassessed in the light of findings presented at the June meeting of the Organisation for Human Brain Mapping in Brighton. Two studies, one using PET and the other using fMRI, showed that that the visual cortical area, V5, responds to a moving tactile stimulus as well as to visual motion. These findings shed light on how the brain combines information from different senses. Francis McGlone, who collaborated on both studies, explained to TICS, ‘we sense the motion of objects through sight, sound and touch and like many perceptual operations, sensations from two or more different modalities can combine to produce a unified percept. There are various possible ways in which the brain might do this. Our findings provide evidence for the existence of a neuroanatomical convergence of both tactile and visual processing of motion in the human MT/V5 complex, an area with known specialization for visual motion processing. To the best of our knowledge, these data provide among the first evidence that MT participates in tactile processing.’ HJB
Rumelhart Prize winner announced The first recipient of the David E. Rumelhart Prize for contributions to the formal analysis of human cognition is Geoffrey E. Hinton,
1364-6613/01/$ – see front matter © 2001 Elsevier Science Ltd. All rights reserved.
In Brief articles written by Heidi Johansen-Berg Mark Wexler and Dominic Palmer-Brown
TRENDS in Cognitive Sciences Vol.5 No.8 August 2001
331
In Brief
We’ve all got rhythm The timing of rhythmic actions, such as finger tapping, is sensitive to temporal differences below the level of conscious detection, according to new research [J. Exp. Psychol. Hum. Percept. Perform. (2001) 27, 600–621]. Bruno Repp and colleagues asked people to tap along to an auditory rhythm. Without telling his subjects, Repp occasionally altered the timing of the beat very slightly. These changes were so subtle that subjects did not consciously perceive any alteration in rhythm. However, they accurately updated their finger movements in response to the change. This suggests that the brain contains a timekeeper that can use subliminal timing information to control movement accurately. HJB
Bugs in odometry Desert ants can perform a remarkable feat of navigation – after travelling a complex path, they ‘know’ the exact direction and distance to their home base. In order to perform this navigational task, ants need to integrate both their rotation and translation, updating their position vector with respect to the nest. How ants measure linear distance travelled – their ‘odometer’ – has been unknown. However, Sandra Wohlgemuth and her colleagues [Nature (2001) 411, 795–798] have recently discovered that the odometer of the genus Cataglyphis is sophisticated enough to take the third dimension into account. When ants travel along a steep slope, they count distance along the ground, rather than the length of their path: when they return home on flat terrain, they compensate for ground distance, rather than for path length. Wohlgemuth et al. showed that this compensation for ups and downs does not use tricks based on energy expenditure, travel time, or optic flow, and therefore must be based on the perception of the ant’s angle with respect to the direction of gravity. Will they send ants into space to make sure? MW
Bugs in vision Most non-experts naively believe that what they see accurately reflects what they look at, much as a photographic image faithfully portrays a scene. Hence the interest of visual illusions, which, by exposing the subtle ‘bugs’ of vision, demonstrate the complexity of http://tics.trends.com
constructing a visual representation of the world. Recently, however, Yoram Bonneh and his co-workers [Nature (2001) 411, 798–801] have uncovered a most unsubtle and embarrassingly visible bug in vision: bright steady objects, superimposed over a moving field, seem to disappear for several seconds as one looks at them (demonstrations can be downloaded at http://www.weizmann.ac.il/ ~masagi/MIB/mib.html). This motioninduced blindness effect, which occurs under normal viewing conditions and for a variety of stimulus parameters, subjectively feels as though the disappearing objects suddenly entered the retinal blind spot. In recent years, a variety of ‘attentional blindness’ effects have shown that we can miss even quite important changes, unless we pay close attention. The originality of motioninduced blindness is that it results in actual disappearance of objects, even when we pay attention to them. MW
Neglecting the temporal lobe One of the first things today’s student of cognitive neuroscience learns is the ‘what and where’ doctrine: the temporal lobe processes information about form whereas the parietal lobe processes information about space. This doctrine is strengthened by centuries of documented cases of hemispatial visual neglect – a deficit in spatial awareness thought to occur after parietal lobe damage. However, these ideas are challenged by a recent study that analysed the locations of lesions in a group of patients who had neglect, with or without additional visual deficits [Nature (2001) 411, 950–953]. Detailed analysis revealed that pure neglect (without associated visual defects) was associated with damage to the superior temporal cortex; damage to the posterior parietal cortex was associated only with visual field blindness. This finding could reconcile the discrepancy between the human data and the animal literature where neglect is only observed after damage to the superior temporal cortex. HJB
who will receive the award in August in Edinburgh, at the Annual Meeting of the Cognitive Science Society (www.hcrc.ed.ac.uk/cogsci2001). He will deliver the Prize Lecture, on designing generative models, at the meeting. Hinton is currently Director of the Gatsby Computational Neuroscience Unit at UCL and is an obvious choice for the award, having made several groundbreaking contributions to the analysis of representation, processing and learning in neural networks. The prize (www.cnbc.cmu.edu/derprize) will now be awarded annually, instead of biennially, because of the significant number of outstanding candidates, and the second recipient will be announced at the Edinburgh meeting. DPB
Tactile motion activates V5 Current thinking on the type of inputs that drive ‘visual’ areas might need to be reassessed in the light of findings presented at the June meeting of the Organisation for Human Brain Mapping in Brighton. Two studies, one using PET and the other using fMRI, showed that that the visual cortical area, V5, responds to a moving tactile stimulus as well as to visual motion. These findings shed light on how the brain combines information from different senses. Francis McGlone, who collaborated on both studies, explained to TICS, ‘we sense the motion of objects through sight, sound and touch and like many perceptual operations, sensations from two or more different modalities can combine to produce a unified percept. There are various possible ways in which the brain might do this. Our findings provide evidence for the existence of a neuroanatomical convergence of both tactile and visual processing of motion in the human MT/V5 complex, an area with known specialization for visual motion processing. To the best of our knowledge, these data provide among the first evidence that MT participates in tactile processing.’ HJB
Rumelhart Prize winner announced The first recipient of the David E. Rumelhart Prize for contributions to the formal analysis of human cognition is Geoffrey E. Hinton,
1364-6613/01/$ – see front matter © 2001 Elsevier Science Ltd. All rights reserved.
In Brief articles written by Heidi Johansen-Berg Mark Wexler and Dominic Palmer-Brown