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Textural complexity
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Whorfian reasoning What is the relationship between language and cognition? One possibility, popularly associated with Benjamin Lee Whorf, is that people’s cognition is profoundly influenced by their native language and predicts, therefore, that speakers of different languages will manifest different ways of thinking. Early investigations of this claim were less than promising; for example, Berlin and Kay1 found that people who spoke languages with very few color terms were nonetheless able to discriminate a full range of colors, but the last decade has seen renewed interest in this question. A recent paper by Pederson et al.2
exemplifies the new wave of Whorfian research. Their investigation focuses on the influence of spatial language on spatial perception. Languages vary in how they code space: English generally relies on a relative coordinate system (‘right’, ‘left’; ‘up’, ‘down’) while the Australian language, Arandic, uses an absolute system (‘north’, ‘south’). The researchers established the dominant means of spatial coding for 13 languages using an elicitation task. They then conducted a non-linguistic spatial reasoning task (imitating the ordering of objects in a row) which could plausibly be interpreted in either an ab-
Textural complexity The human temporal cortex is known to be involved in visual learning and memory, but its role in visual perception is poorly understood. Studies in macaque monkeys have shown the temporal cortex to have a critical role in complex shape and texture discrimination. Recently, Huxlin and Merigan tested whether the human temporal cortex is involved in similar tasks by investigating deficits in complex textureand luminance-based visual discrimination in three patients with temporal lobe lesions. They showed that patient performance (relative to age-matched controls) was specifically affected in tasks involving the perception of texture-based shapes. When shapes were defined by luminance cues, perform-
ance was in the normal range or slightly decreased. Interestingly, the discrimination deficits were not restricted to the hemifield contralateral to the lesion site, but occurred equivalently in both visual hemifields. These results are in agreement with data from electrophysiological recordings in monkeys, although the authors emphasize the limited knowledge we have about the homologies between the human and monkey temporal cortex. Finally, it has to be noted that the test of patient performance in object naming based on line drawings did not yield a deficit. This suggests that the temporal lobectomy patients studied in this experiment were impaired only in making subtle visual discriminations, involving
Speed and dyslexia A person with developmental dyslexia typically has deficits in his/her reading ability that cannot be accounted for by factors such as brain injury, motivation, sensory acuity, or scholastic exposure. There is an active ongoing debate regarding the possible role of an inadequacy in the magnocellular (M) visual pathway as a causative factor for this disorder. In primates, fast-moving, low-contrast visual information is processed by the magnocellular subdivision of the visual system. The M pathway is primarily involved in processing motion and depth perception, stereoscopic vision, and in locating objects in space. Demb et al. now report some interesting psychophysical data that might suggest that dyslexia is indeed related to an M pathway deficiency1. The authors administered five reading measures from the Wide Range Achievement Test (WRAT3) and found that dyslexic subjects had significantly higher psychophysical thresholds than controls in speed discrimination tasks, including spelling and comprehension tasks, non-word reading, and reading
rate. These findings provide a psychophysical complement to the anatomical findings of Livingstone et al. who observed abnormalities within the magnocellular layers of the lateral geniculate nuclei in dyslexic brains2. Given the small number of subjects in the latest study these results should be regarded as preliminary; however, they do provide some interesting questions for future research. For example, can words be presented in such a fashion as to side-step the Mpathway deficiencies in dyslexic subjects? Can motion discrimination tasks provide a more sensitive psychophysical predictor of dyslexia? The answers to these questions may lead to therapeutic and experimental advances in this area. References 1 Demb, J.B. et al. (1998) Psychophysical evidence for magnocellular pathway deficits in dyslexia
solute or relative spatial way. A correlation was found between subjects’ dominant linguistic means of coding space and their preferred way of solving the non-linguistic spatial task. This paper is unlikely to remain the last word in neo-Whorfian research. However, it sets a high standard, both in terms of the number of languages considered and in terms of the separation of the linguistic and non-linguistic tasks, for future research. References 1 Berlin, B. and Kay, P. (1969) Basic Color Terms, University of California Press 2 Pederson, E. et al. (1998) Semantic typology and spatial conceptualization Language 74, 557–589
complex shapes and/or fine textures. This result is interesting in the light of the localization of the lesions in these patients. Although it is not specifically stated, it seems that their lesions are restricted to the lateral surface of one temporal lobe, mainly in its anterior half. Perhaps this explains the discrepancy between the findings of Huxlin and Merigan in the object naming task and data from visual agnosic patients, whose lesions are usually more ventral and who fail this task. This study proposes that the temporal cortex plays a role in texture-based information processing that may explain its function in specifically complex visual perception. Reference 1 Huxlin, K.R and Merigan, W.H. (1998) Deficits in complex visual perception following unilateral temporal lobectomy J. Cogn. Neurosci. 10, 395–407
Thalamic motion The thalamus has traditionally been thought of as a passive relay station for sensory input en route to the cortex. But a recent report adds support to growing evidence that the thalamus might actively participate in the processing of some sensory information. Merabet et al.1 have shown that neurons in cat pulvinar (in the lateralposterior subdivision) can signal the direction of a moving plaid stimulus, whose motion is the vector sum of two gratings drifting in different directions. This is the first time a sub-cortical nucleus has been implicated in complex motion computations, and suggests that thalamo–cortical loops play a part in the dynamic processing of sensory signals.
Vis. Res. 38, 1555–1559 2 Livingstone, M.S. et al. (1991) Physiological and anatomical evidence for a magnocellular
Reference 1 Merabet, L. et al. (1998) Motion integration
defect in developmental dyslexia Proc. Natl.
in a thalamic visual nucleus Nature 396,
Acad. Sci. U. S. A. 88, 7943–7947
265–268
1364-6613/99/$ – see front matter © 1999 Elsevier Science. All rights reserved. Trends in Cognitive Sciences – Vol. 3, No. 1,
January 1999
3
Whorfian reasoning What is the relationship between language and cognition? One possibility, popularly associated with Benjamin Lee Whorf, is that people’s cognition is profoundly influenced by their native language and predicts, therefore, that speakers of different languages will manifest different ways of thinking. Early investigations of this claim were less than promising; for example, Berlin and Kay1 found that people who spoke languages with very few color terms were nonetheless able to discriminate a full range of colors, but the last decade has seen renewed interest in this question. A recent paper by Pederson et al.2
exemplifies the new wave of Whorfian research. Their investigation focuses on the influence of spatial language on spatial perception. Languages vary in how they code space: English generally relies on a relative coordinate system (‘right’, ‘left’; ‘up’, ‘down’) while the Australian language, Arandic, uses an absolute system (‘north’, ‘south’). The researchers established the dominant means of spatial coding for 13 languages using an elicitation task. They then conducted a non-linguistic spatial reasoning task (imitating the ordering of objects in a row) which could plausibly be interpreted in either an ab-
Textural complexity The human temporal cortex is known to be involved in visual learning and memory, but its role in visual perception is poorly understood. Studies in macaque monkeys have shown the temporal cortex to have a critical role in complex shape and texture discrimination. Recently, Huxlin and Merigan tested whether the human temporal cortex is involved in similar tasks by investigating deficits in complex textureand luminance-based visual discrimination in three patients with temporal lobe lesions. They showed that patient performance (relative to age-matched controls) was specifically affected in tasks involving the perception of texture-based shapes. When shapes were defined by luminance cues, perform-
ance was in the normal range or slightly decreased. Interestingly, the discrimination deficits were not restricted to the hemifield contralateral to the lesion site, but occurred equivalently in both visual hemifields. These results are in agreement with data from electrophysiological recordings in monkeys, although the authors emphasize the limited knowledge we have about the homologies between the human and monkey temporal cortex. Finally, it has to be noted that the test of patient performance in object naming based on line drawings did not yield a deficit. This suggests that the temporal lobectomy patients studied in this experiment were impaired only in making subtle visual discriminations, involving
Speed and dyslexia A person with developmental dyslexia typically has deficits in his/her reading ability that cannot be accounted for by factors such as brain injury, motivation, sensory acuity, or scholastic exposure. There is an active ongoing debate regarding the possible role of an inadequacy in the magnocellular (M) visual pathway as a causative factor for this disorder. In primates, fast-moving, low-contrast visual information is processed by the magnocellular subdivision of the visual system. The M pathway is primarily involved in processing motion and depth perception, stereoscopic vision, and in locating objects in space. Demb et al. now report some interesting psychophysical data that might suggest that dyslexia is indeed related to an M pathway deficiency1. The authors administered five reading measures from the Wide Range Achievement Test (WRAT3) and found that dyslexic subjects had significantly higher psychophysical thresholds than controls in speed discrimination tasks, including spelling and comprehension tasks, non-word reading, and reading
rate. These findings provide a psychophysical complement to the anatomical findings of Livingstone et al. who observed abnormalities within the magnocellular layers of the lateral geniculate nuclei in dyslexic brains2. Given the small number of subjects in the latest study these results should be regarded as preliminary; however, they do provide some interesting questions for future research. For example, can words be presented in such a fashion as to side-step the Mpathway deficiencies in dyslexic subjects? Can motion discrimination tasks provide a more sensitive psychophysical predictor of dyslexia? The answers to these questions may lead to therapeutic and experimental advances in this area. References 1 Demb, J.B. et al. (1998) Psychophysical evidence for magnocellular pathway deficits in dyslexia
solute or relative spatial way. A correlation was found between subjects’ dominant linguistic means of coding space and their preferred way of solving the non-linguistic spatial task. This paper is unlikely to remain the last word in neo-Whorfian research. However, it sets a high standard, both in terms of the number of languages considered and in terms of the separation of the linguistic and non-linguistic tasks, for future research. References 1 Berlin, B. and Kay, P. (1969) Basic Color Terms, University of California Press 2 Pederson, E. et al. (1998) Semantic typology and spatial conceptualization Language 74, 557–589
complex shapes and/or fine textures. This result is interesting in the light of the localization of the lesions in these patients. Although it is not specifically stated, it seems that their lesions are restricted to the lateral surface of one temporal lobe, mainly in its anterior half. Perhaps this explains the discrepancy between the findings of Huxlin and Merigan in the object naming task and data from visual agnosic patients, whose lesions are usually more ventral and who fail this task. This study proposes that the temporal cortex plays a role in texture-based information processing that may explain its function in specifically complex visual perception. Reference 1 Huxlin, K.R and Merigan, W.H. (1998) Deficits in complex visual perception following unilateral temporal lobectomy J. Cogn. Neurosci. 10, 395–407
Thalamic motion The thalamus has traditionally been thought of as a passive relay station for sensory input en route to the cortex. But a recent report adds support to growing evidence that the thalamus might actively participate in the processing of some sensory information. Merabet et al.1 have shown that neurons in cat pulvinar (in the lateralposterior subdivision) can signal the direction of a moving plaid stimulus, whose motion is the vector sum of two gratings drifting in different directions. This is the first time a sub-cortical nucleus has been implicated in complex motion computations, and suggests that thalamo–cortical loops play a part in the dynamic processing of sensory signals.
Vis. Res. 38, 1555–1559 2 Livingstone, M.S. et al. (1991) Physiological and anatomical evidence for a magnocellular
Reference 1 Merabet, L. et al. (1998) Motion integration
defect in developmental dyslexia Proc. Natl.
in a thalamic visual nucleus Nature 396,
Acad. Sci. U. S. A. 88, 7943–7947
265–268
1364-6613/99/$ – see front matter © 1999 Elsevier Science. All rights reserved. Trends in Cognitive Sciences – Vol. 3, No. 1,
January 1999
3