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Long-haul brain drain
286
News & Comment
TRENDS in Cognitive Sciences Vol.5 No.7 July 2001
In Brief
Know thine own action
Long-haul brain drain
To what extent can we recognize self-generated actions from those performed by others, when observing their visual effects? In a recent study, Knoblich and Prinz [J. Exp. Psychol. Hum. Percept. Perform. 27, 456–465] found that subjects could do so, in a task in which they first drew or traced familiar and unfamiliar characters without visual feedback. A week later (to eliminate short-term memory influences), the same subjects watched kinematic displays of their own movements, or those produced by others. Surprisingly, subjects could distinguish their own traces reliably better than chance, for unfamiliar as well as familiar characters, even when overall size and duration of the traces were eliminated as possible cues. The conclusion is that people recognize their own movements from their detailed kinematic properties. The authors argue that this result is evidence for a contribution of motor planning mechanisms to perception, and for a common coding in the brain for perception and action. MW
Perception of danger – black and white? What has led to recent police shootings of unarmed blacks? A recent study of perceptual biases by Keith Payne [to appear in the August issue of the Journal of Personality and Social Psychology], suggests that the cause lies deep. In Payne’s study, subjects – all of whom were university students – identified pictures of weapons or non-violent tools. After watching photographs of black faces, subjects were quicker to identify weapons; after watching white faces, on the other hand, subjects were quicker to identify tools. When judgments had to be made very rapidly – as would be the case by a police officer in a dangerous situation – subjects were more likely to mistakenly perceive a tool as a weapon after viewing black faces than after viewing white faces. ‘The fact that this effect is “automatic” in the sense that people cannot “turn it off” even when they try is striking and disturbing’, Payne said. ‘This study is surprising because it shows that racial biases are difficult to control even among relatively well-educated, open-minded and liberal college students.’ MW http://tics.trends.com
Too much jet setting can shrink your brain and impair your cognitive ability, according to new research by Kwangwook Cho [Nature Neurosci. (2001) 4, 567–568]. Brain scans showed that airline cabin crew who had less than five days to recover between long-haul flights had smaller right temporal lobes than those who were allowed longer recovery times. The short recovery group also performed worse on a spatial memory test that depends on the temporal lobe. The brain shrinkage was correlated with elevated levels of cortisol. Cho suggests that frequent shifts between time zones without sufficient time for readjustment disrupts the delicate relationship between the day–night cycle and our bodies’ circadian rhythms, leading to increased cortisol levels. As Cho explained to TICS, ‘disruption of circadian rhythms causes physiological and physical stress and high stress levels have an impact on brain function. Brain atrophy may be caused by high stress hormone levels.’ The airline crew study suggests that after five years of increased cortisol, cognitive deficits and brain shrinkage become apparent. HJB
Visual cortex represents invisible lines If fine lines are drawn close enough together the separate lines become invisible and we perceive only a blur. Where does this limit to our vision occur? For a long time researchers thought that optical blurring at the eye was largely to blame and that information about very fine lines got no further than the retina. However, Sheng He and Donald MacLeod now suggest that fine detail, invisible to the eye, can penetrate as far as the visual cortex
[Nature (2001), 411, 473–476]. They took advantage of a well-known visual ‘aftereffect’ to demonstrate this: after viewing a pattern of horizontal lines for several seconds, subjects are worse at perceiving a second pattern of horizontal lines than a second pattern of vertical lines. This is because the visual cortex contains orientation-selective cells and the cells that prefer horizontal lines are fatigued by responding to the first pattern and so slower to respond again to a second horizontal pattern. The researchers showed that this aftereffect occurred even if the first pattern was so fine that the orientation of the lines was invisible to the subject. Because the aftereffect is due to activity of orientation-selective cells, which first appear in visual cortex, its presence implies that information about line orientation gets as far as the visual cortex but in this case does not enter conscious awareness. HJB
The effect of affect One of the functions of emotion is presumed to be the enhancement of important stimuli, which could aid their detection. In the human brain, this perceptual modulation by emotion is thought to be grounded in the amygdala. Anderson and Phelps [Nature, 411, 305–309] have demonstrated the role of amygdala by studying perceptual detection in a patient with damage in this brain structure. The authors made use of the so-called ‘attentional blink’ effect, in which the detection of a target by healthy subjects is temporarily impeded immediately after detecting another stimulus; however, when the target is an emotionally charged word, such as ‘bastard’ or ‘rape’, its detection is enhanced and the attentional blink is partly overcome. Although the patient with amygdala damage had an attentional blink similar to healthy subjects on emotionally neutral terms, she showed no enhancement for detecting emotionally aversive words, nor any modulation of the attentional blink by emotional factors. These results underline the role of the amygdala in bringing urgent information to awareness. MW
1364-6613/01/$ – see front matter © 2001 Elsevier Science Ltd. All rights reserved.
In Brief articles written by Heidi Johansen-Berg and Mark Wexler
News & Comment
TRENDS in Cognitive Sciences Vol.5 No.7 July 2001
In Brief
Know thine own action
Long-haul brain drain
To what extent can we recognize self-generated actions from those performed by others, when observing their visual effects? In a recent study, Knoblich and Prinz [J. Exp. Psychol. Hum. Percept. Perform. 27, 456–465] found that subjects could do so, in a task in which they first drew or traced familiar and unfamiliar characters without visual feedback. A week later (to eliminate short-term memory influences), the same subjects watched kinematic displays of their own movements, or those produced by others. Surprisingly, subjects could distinguish their own traces reliably better than chance, for unfamiliar as well as familiar characters, even when overall size and duration of the traces were eliminated as possible cues. The conclusion is that people recognize their own movements from their detailed kinematic properties. The authors argue that this result is evidence for a contribution of motor planning mechanisms to perception, and for a common coding in the brain for perception and action. MW
Perception of danger – black and white? What has led to recent police shootings of unarmed blacks? A recent study of perceptual biases by Keith Payne [to appear in the August issue of the Journal of Personality and Social Psychology], suggests that the cause lies deep. In Payne’s study, subjects – all of whom were university students – identified pictures of weapons or non-violent tools. After watching photographs of black faces, subjects were quicker to identify weapons; after watching white faces, on the other hand, subjects were quicker to identify tools. When judgments had to be made very rapidly – as would be the case by a police officer in a dangerous situation – subjects were more likely to mistakenly perceive a tool as a weapon after viewing black faces than after viewing white faces. ‘The fact that this effect is “automatic” in the sense that people cannot “turn it off” even when they try is striking and disturbing’, Payne said. ‘This study is surprising because it shows that racial biases are difficult to control even among relatively well-educated, open-minded and liberal college students.’ MW http://tics.trends.com
Too much jet setting can shrink your brain and impair your cognitive ability, according to new research by Kwangwook Cho [Nature Neurosci. (2001) 4, 567–568]. Brain scans showed that airline cabin crew who had less than five days to recover between long-haul flights had smaller right temporal lobes than those who were allowed longer recovery times. The short recovery group also performed worse on a spatial memory test that depends on the temporal lobe. The brain shrinkage was correlated with elevated levels of cortisol. Cho suggests that frequent shifts between time zones without sufficient time for readjustment disrupts the delicate relationship between the day–night cycle and our bodies’ circadian rhythms, leading to increased cortisol levels. As Cho explained to TICS, ‘disruption of circadian rhythms causes physiological and physical stress and high stress levels have an impact on brain function. Brain atrophy may be caused by high stress hormone levels.’ The airline crew study suggests that after five years of increased cortisol, cognitive deficits and brain shrinkage become apparent. HJB
Visual cortex represents invisible lines If fine lines are drawn close enough together the separate lines become invisible and we perceive only a blur. Where does this limit to our vision occur? For a long time researchers thought that optical blurring at the eye was largely to blame and that information about very fine lines got no further than the retina. However, Sheng He and Donald MacLeod now suggest that fine detail, invisible to the eye, can penetrate as far as the visual cortex
[Nature (2001), 411, 473–476]. They took advantage of a well-known visual ‘aftereffect’ to demonstrate this: after viewing a pattern of horizontal lines for several seconds, subjects are worse at perceiving a second pattern of horizontal lines than a second pattern of vertical lines. This is because the visual cortex contains orientation-selective cells and the cells that prefer horizontal lines are fatigued by responding to the first pattern and so slower to respond again to a second horizontal pattern. The researchers showed that this aftereffect occurred even if the first pattern was so fine that the orientation of the lines was invisible to the subject. Because the aftereffect is due to activity of orientation-selective cells, which first appear in visual cortex, its presence implies that information about line orientation gets as far as the visual cortex but in this case does not enter conscious awareness. HJB
The effect of affect One of the functions of emotion is presumed to be the enhancement of important stimuli, which could aid their detection. In the human brain, this perceptual modulation by emotion is thought to be grounded in the amygdala. Anderson and Phelps [Nature, 411, 305–309] have demonstrated the role of amygdala by studying perceptual detection in a patient with damage in this brain structure. The authors made use of the so-called ‘attentional blink’ effect, in which the detection of a target by healthy subjects is temporarily impeded immediately after detecting another stimulus; however, when the target is an emotionally charged word, such as ‘bastard’ or ‘rape’, its detection is enhanced and the attentional blink is partly overcome. Although the patient with amygdala damage had an attentional blink similar to healthy subjects on emotionally neutral terms, she showed no enhancement for detecting emotionally aversive words, nor any modulation of the attentional blink by emotional factors. These results underline the role of the amygdala in bringing urgent information to awareness. MW
1364-6613/01/$ – see front matter © 2001 Elsevier Science Ltd. All rights reserved.
In Brief articles written by Heidi Johansen-Berg and Mark Wexler