2008 Woodie Awards
Brain uses sense of touch to see the world
Issue date: 4/3/08
The researchers considered other variables that might enhance or detract from the processing of orientation discrimination.
For example, the degree of indentation caused by the pins into the finger was changed in one experiment. Also, the speed at which the bar passed over the pins was considered an important factor.
Interestingly, the amount of pin indentation and the speed resulted in only marginal effects on the subjects' ability to distinguish angles.
This important finding suggests that cortical neurons are able to maintain consistent perception of the orientation despite other changes in the stimulus.
The main discovery of these tactile perception experiments was that the human threshold for distinguishing between angular orientations is about 20 degrees.
This means that a person could distinguish between a line at 20 degrees and at 40 degrees but will be unlikely to detect a difference between 20 and 30 degree lines.
The Mind/Brain Institute researchers also observed that orientation acuity was highest for horizontal stimuli, when a bar at zero degrees was simulated by the fingerpad.
This contradicts previous findings that there was greater tactile sensitivity for both horizontal and vertical stimuli, and the least amount of detection at an oblique angle like 45 degrees.
Yet this recent publication finds that there is a smaller angular threshold for horizontal stimuli rather than vertical ones.
This means that it is easier for a finger to distinguish between bars that are both around zero degrees and that it becomes harder to distinguish between bars around 90 degrees, or parallel with the finger.
Studying the response to different orientations of stimuli leads to greater understanding of the cortical processing of sensory inputs. Our sense of touch allows us to experience the texture, temperature, size, orientation and shape of objects in the world.
Further research into how we experience shape raises interesting questions about how the visual and tactile systems may differentially process information as well as how higher-level processing may piece together all of these different aspects in order to create a complete sensory experience of our surroundings.
For example, the degree of indentation caused by the pins into the finger was changed in one experiment. Also, the speed at which the bar passed over the pins was considered an important factor.
Interestingly, the amount of pin indentation and the speed resulted in only marginal effects on the subjects' ability to distinguish angles.
This important finding suggests that cortical neurons are able to maintain consistent perception of the orientation despite other changes in the stimulus.
The main discovery of these tactile perception experiments was that the human threshold for distinguishing between angular orientations is about 20 degrees.
This means that a person could distinguish between a line at 20 degrees and at 40 degrees but will be unlikely to detect a difference between 20 and 30 degree lines.
The Mind/Brain Institute researchers also observed that orientation acuity was highest for horizontal stimuli, when a bar at zero degrees was simulated by the fingerpad.
This contradicts previous findings that there was greater tactile sensitivity for both horizontal and vertical stimuli, and the least amount of detection at an oblique angle like 45 degrees.
Yet this recent publication finds that there is a smaller angular threshold for horizontal stimuli rather than vertical ones.
This means that it is easier for a finger to distinguish between bars that are both around zero degrees and that it becomes harder to distinguish between bars around 90 degrees, or parallel with the finger.
Studying the response to different orientations of stimuli leads to greater understanding of the cortical processing of sensory inputs. Our sense of touch allows us to experience the texture, temperature, size, orientation and shape of objects in the world.
Further research into how we experience shape raises interesting questions about how the visual and tactile systems may differentially process information as well as how higher-level processing may piece together all of these different aspects in order to create a complete sensory experience of our surroundings.
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