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Attention in the ventral pathway?
Update Monitor Summaries of recently published papers of interest to cognitive scientists. Readers who would like to contribute to this section, by identifying appropriate papers and writing short summaries, should contact the Editor ([email protected]).
Attention in the ventral pathway? In real life, as opposed to laboratory experiments, multiple objects in the visual scene compete for attention, such that behaviourally relevant objects are processed at the expense of irrelevant objects. How this is achieved in terms of cortical activity is the topic of much current research, and the detailed map of visual areas in the macaque and their interconnections1 has aided greatly in the search for cortical regions that might have a role in visual attention. In a recent experiment, De Weerd and colleagues examined the possible role of two extrastriate visual areas, V4 and TEO, in attention2. These two regions are part of the ‘ventral’ pathway through extrastriate cortex, which is important for object recognition in primates, although it has also been shown that responses of neurons in V4 and TEO are modulated by the attentional demands of many different visual task. De Weerd et al. tested directly the role of these areas in visual attention by making lesions in the cortex of two macaques, such that a lesion of V4 affected one quadrant of the visual field, a lesion of TEO affected another quadrant, with combined lesions of both areas affecting a third quadrant. The remaining quadrant was intact, thus serving as a control. The monkeys were trained on an orientation-discrimination task, and, in blocks of trials, were presented with grating stimuli away from the fixation point, in each of the visual quadrants in turn. In further blocks of trials, distractor discs surrounding the target grating were added to the visual display. Measurements of discrimination thresholds revealed a marked attentional effect in the areas of visual field corresponding to the extrastriate lesions compared with the normal quadrant. Orientation discrimination was good
with or without distractors present in the normal quadrant; discrimination thresholds were somewhat higher in the other three quadrants but, crucially, the presence of distractors raised these thresholds markedly, with the strongest effect in the quadrant affected by the combined V4/TEO lesion. These effects were also found to be contrastdependent, with increasing distractor contrast producing greater deficits in task performance. These results show clearly that extrastriate areas in temporal cortex have a role in visual attention. But the size of the attentional deficit when those areas are removed was even more striking than expected – because of the multiple interconnections between visual areas, it might be expected that the loss of one area would be easily compensated for by remaining interconnected areas. One possible explanation for the apparent lack of compensation is that the role of V4 and TEO in attention is task-specific. Even if other areas, such as those in the dorsal stream, were able to compensate for the ventral-stream lesions, they might not be able to do so for an orientation-discrimination task, which has been supposed to be a ‘ventral-stream function’. Further experiments might reveal whether ventral lesions also affect ‘dorsal-stream functions’, such as motion discrimination – then it might be possible to say whether or not the ventral extrastriate cortex has a more global attentional role. References 1 Felleman, D.J. and Van Essen, D.C. (1991) Distributed hierarchical processing in primate cerebral cortex Cereb. Cortex 1, 1–47 2 De Weerd, P. et al. (1999) Loss of attentional stimulus selection after extrastriate cortical lesions in macaques Nat. Neurosci. 2, 753–758
Face up to the fusiform gyrus The fundamental question of whether the visual processes underlying the recognition of human faces are unique, in contrast to other complex visual stimuli, has been intensely studied. To examine this issue, neuroimaging, physiological and behavioral studies often focus on the ventral occipitotemporal pathway; in particular, a region in the fusiform gyrus known as the fusiform face area (FFA). Significant results from such studies suggest that this region is specialized for the perception of human faces. In a recent neuroimaging study Kanwisher et al. report data supporting the existence of a human FFA that is selective for face processing1. The authors used eight different stimuli and recorded the strongest FFA response when subjects
viewed human faces rather than control stimuli of human heads, whole humans or animal heads. Although the FFA responded to stimuli other than human faces, the responses were dominated by face stimuli rather than nonface stimuli. These results suggest a specialized face-processing region, whilst not ruling out the discovery of other face-responsive areas. While significant progress has been made in understanding specific aspects of face-recognition, a comprehensive understanding of just how ‘special’ this process is still eludes us.
Discordant views on the ‘Mozart effect’ Research reported by Rauscher et al. in 1993 suggested that listening to music by Mozart improved performance on an intelligence test1. That is, after listening to Mozart’s Sonata for Two Pianos in D Major, K. 448 for 10 minutes, university undergraduates demonstrated a temporary increase of 9 IQ points on a spatial subtest of the Stanford–Binet Intelligence Test). The research was motivated by a theory of higher-level brain function which proposed that exposure to complex music could activate or prime neural firing patterns similar to those used in spatial–temporal reasoning. This surprising result became known as the ‘Mozart effect’. However, two recent studies suggest that the Mozart effect falls flat. In a meta-analysis of 17 studies, Chabris2 showed that the effect was less than would have arisen by chance, though it may exert a small positive effect on some ‘spatial’ tasks, such as the Paper Folding and Cutting subtest used in the original study. In the same issue as Chabris’ report, there is combined report from three independent research groups who each tried, without success, to replicate the Mozart effect under comparable conditions3. In none of the studies was there any statistically reliable evidence for the Mozart effect; that is, subjects performed as well on spatial-reasoning tasks whether they listened to Mozart, silence, minimalist music, ‘relaxation’ music or had relaxation instructions. In a reply to these reports, though, Rauscher addresses some misconceptions that she suggests have surrounded attempts to replicate the Mozart effect, and acknowledges that the original effect cannot be found under all laboratory conditions4. She also points to other studies that have found a Mozart effect for spatial-reasoning tasks, and one in which an effect was found in the EEG of comatose epileptic patients. Although the recent results reported by Chabris and by Steele et al. suggest that a requiem for the Mozart effect may be in order, it appears that the final movement has not yet been written… References 1 Rauscher, F.H., Shaw, G.L. and Ky, K.N. (1993) Music and spatial task performance Nature 365, 611 2 Chabris, C.F. (1999) Prelude or requiem for the ‘Mozart effect’? Nature 400, 826–827 3 Steele, K.M. et al. (1999) Prelude or requiem
Reference 1 Kanwisher, N. et al. (1999) The fusiform face area is selective for faces not animals NeuroReport 10, 183–187
for the ‘Mozart effect’? Nature 400, 827 4 Rauscher, F.H. (1999) Prelude or requiem for the ‘Mozart effect’? Reply Nature 400, 827–828
1364-6613/99/$ – see front matter © 1999 Elsevier Science Ltd. All rights reserved. Trends in Cognitive Sciences – Vol. 3, No. 11,
November 1999
409
Attention in the ventral pathway? In real life, as opposed to laboratory experiments, multiple objects in the visual scene compete for attention, such that behaviourally relevant objects are processed at the expense of irrelevant objects. How this is achieved in terms of cortical activity is the topic of much current research, and the detailed map of visual areas in the macaque and their interconnections1 has aided greatly in the search for cortical regions that might have a role in visual attention. In a recent experiment, De Weerd and colleagues examined the possible role of two extrastriate visual areas, V4 and TEO, in attention2. These two regions are part of the ‘ventral’ pathway through extrastriate cortex, which is important for object recognition in primates, although it has also been shown that responses of neurons in V4 and TEO are modulated by the attentional demands of many different visual task. De Weerd et al. tested directly the role of these areas in visual attention by making lesions in the cortex of two macaques, such that a lesion of V4 affected one quadrant of the visual field, a lesion of TEO affected another quadrant, with combined lesions of both areas affecting a third quadrant. The remaining quadrant was intact, thus serving as a control. The monkeys were trained on an orientation-discrimination task, and, in blocks of trials, were presented with grating stimuli away from the fixation point, in each of the visual quadrants in turn. In further blocks of trials, distractor discs surrounding the target grating were added to the visual display. Measurements of discrimination thresholds revealed a marked attentional effect in the areas of visual field corresponding to the extrastriate lesions compared with the normal quadrant. Orientation discrimination was good
with or without distractors present in the normal quadrant; discrimination thresholds were somewhat higher in the other three quadrants but, crucially, the presence of distractors raised these thresholds markedly, with the strongest effect in the quadrant affected by the combined V4/TEO lesion. These effects were also found to be contrastdependent, with increasing distractor contrast producing greater deficits in task performance. These results show clearly that extrastriate areas in temporal cortex have a role in visual attention. But the size of the attentional deficit when those areas are removed was even more striking than expected – because of the multiple interconnections between visual areas, it might be expected that the loss of one area would be easily compensated for by remaining interconnected areas. One possible explanation for the apparent lack of compensation is that the role of V4 and TEO in attention is task-specific. Even if other areas, such as those in the dorsal stream, were able to compensate for the ventral-stream lesions, they might not be able to do so for an orientation-discrimination task, which has been supposed to be a ‘ventral-stream function’. Further experiments might reveal whether ventral lesions also affect ‘dorsal-stream functions’, such as motion discrimination – then it might be possible to say whether or not the ventral extrastriate cortex has a more global attentional role. References 1 Felleman, D.J. and Van Essen, D.C. (1991) Distributed hierarchical processing in primate cerebral cortex Cereb. Cortex 1, 1–47 2 De Weerd, P. et al. (1999) Loss of attentional stimulus selection after extrastriate cortical lesions in macaques Nat. Neurosci. 2, 753–758
Face up to the fusiform gyrus The fundamental question of whether the visual processes underlying the recognition of human faces are unique, in contrast to other complex visual stimuli, has been intensely studied. To examine this issue, neuroimaging, physiological and behavioral studies often focus on the ventral occipitotemporal pathway; in particular, a region in the fusiform gyrus known as the fusiform face area (FFA). Significant results from such studies suggest that this region is specialized for the perception of human faces. In a recent neuroimaging study Kanwisher et al. report data supporting the existence of a human FFA that is selective for face processing1. The authors used eight different stimuli and recorded the strongest FFA response when subjects
viewed human faces rather than control stimuli of human heads, whole humans or animal heads. Although the FFA responded to stimuli other than human faces, the responses were dominated by face stimuli rather than nonface stimuli. These results suggest a specialized face-processing region, whilst not ruling out the discovery of other face-responsive areas. While significant progress has been made in understanding specific aspects of face-recognition, a comprehensive understanding of just how ‘special’ this process is still eludes us.
Discordant views on the ‘Mozart effect’ Research reported by Rauscher et al. in 1993 suggested that listening to music by Mozart improved performance on an intelligence test1. That is, after listening to Mozart’s Sonata for Two Pianos in D Major, K. 448 for 10 minutes, university undergraduates demonstrated a temporary increase of 9 IQ points on a spatial subtest of the Stanford–Binet Intelligence Test). The research was motivated by a theory of higher-level brain function which proposed that exposure to complex music could activate or prime neural firing patterns similar to those used in spatial–temporal reasoning. This surprising result became known as the ‘Mozart effect’. However, two recent studies suggest that the Mozart effect falls flat. In a meta-analysis of 17 studies, Chabris2 showed that the effect was less than would have arisen by chance, though it may exert a small positive effect on some ‘spatial’ tasks, such as the Paper Folding and Cutting subtest used in the original study. In the same issue as Chabris’ report, there is combined report from three independent research groups who each tried, without success, to replicate the Mozart effect under comparable conditions3. In none of the studies was there any statistically reliable evidence for the Mozart effect; that is, subjects performed as well on spatial-reasoning tasks whether they listened to Mozart, silence, minimalist music, ‘relaxation’ music or had relaxation instructions. In a reply to these reports, though, Rauscher addresses some misconceptions that she suggests have surrounded attempts to replicate the Mozart effect, and acknowledges that the original effect cannot be found under all laboratory conditions4. She also points to other studies that have found a Mozart effect for spatial-reasoning tasks, and one in which an effect was found in the EEG of comatose epileptic patients. Although the recent results reported by Chabris and by Steele et al. suggest that a requiem for the Mozart effect may be in order, it appears that the final movement has not yet been written… References 1 Rauscher, F.H., Shaw, G.L. and Ky, K.N. (1993) Music and spatial task performance Nature 365, 611 2 Chabris, C.F. (1999) Prelude or requiem for the ‘Mozart effect’? Nature 400, 826–827 3 Steele, K.M. et al. (1999) Prelude or requiem
Reference 1 Kanwisher, N. et al. (1999) The fusiform face area is selective for faces not animals NeuroReport 10, 183–187
for the ‘Mozart effect’? Nature 400, 827 4 Rauscher, F.H. (1999) Prelude or requiem for the ‘Mozart effect’? Reply Nature 400, 827–828
1364-6613/99/$ – see front matter © 1999 Elsevier Science Ltd. All rights reserved. Trends in Cognitive Sciences – Vol. 3, No. 11,
November 1999
409