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Characterizing spatial tuning functions of neurons in the auditory cortex of young and aged monkeys: a new perspective on old data.

Engle JR, Recanzone GH - Front Aging Neurosci (2013)

Bottom Line: It is also possible that spatial tuning was decreased as a consequence of reduced inhibition at non-best locations.In this report we found that aged animals had greater activity throughout the response period, but primarily during the onset of the response.These results can be interpreted in the context of a failure of the timing and efficiency of feed-forward thalamo-cortical and cortico-cortical circuits in aged animals.

View Article: PubMed Central - PubMed

Affiliation: Department of Psychology and Center for Neuroscience, University of California at Davis Davis, CA, USA ; Evelyn F. McKnight Brain Institute and ARL Division of Neural Systems, Memory and Aging, University of Arizona Tucson, AZ, USA.

ABSTRACT
Age-related hearing deficits are a leading cause of disability among the aged. While some forms of hearing deficits are peripheral in origin, others are centrally mediated. One such deficit is the ability to localize sounds, a critical component for segregating different acoustic objects and events, which is dependent on the auditory cortex. Recent evidence indicates that in aged animals the normal sharpening of spatial tuning between neurons in primary auditory cortex to the caudal lateral field does not occur as it does in younger animals. As a decrease in inhibition with aging is common in the ascending auditory system, it is possible that this lack of spatial tuning sharpening is due to a decrease in inhibition at different periods within the response. It is also possible that spatial tuning was decreased as a consequence of reduced inhibition at non-best locations. In this report we found that aged animals had greater activity throughout the response period, but primarily during the onset of the response. This was most prominent at non-best directions, which is consistent with the hypothesis that inhibition is a primary mechanism for sharpening spatial tuning curves. We also noted that in aged animals the latency of the response was much shorter than in younger animals, which is consistent with a decrease in pre-onset inhibition. These results can be interpreted in the context of a failure of the timing and efficiency of feed-forward thalamo-cortical and cortico-cortical circuits in aged animals. Such a mechanism, if generalized across cortical areas, could play a major role in age-related cognitive decline.

No MeSH data available.


Related in: MedlinePlus

Population first-spike latency. The first-spike latency at each location relative to the best direction is shown for young (gray) and aged (black) monkeys in A1 (circles) and CL (squares) in Panel (A). Aged monkeys had consistently shorter first-spike latencies than young animals. There was also no difference between A1 and CL in aged monkeys, but in young animals latency increased with distance from the best location. (B) Shows the regression between minimum latency and firing rate. There was a significant increase in latency with a decrease in firing rate in younger animals, but this correlation did not exist in aged animals.
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Figure 8: Population first-spike latency. The first-spike latency at each location relative to the best direction is shown for young (gray) and aged (black) monkeys in A1 (circles) and CL (squares) in Panel (A). Aged monkeys had consistently shorter first-spike latencies than young animals. There was also no difference between A1 and CL in aged monkeys, but in young animals latency increased with distance from the best location. (B) Shows the regression between minimum latency and firing rate. There was a significant increase in latency with a decrease in firing rate in younger animals, but this correlation did not exist in aged animals.

Mentions: We also considered how first-spike latency was related to the spatial location of the stimulus. Figure 8A shows the minimum first-spike latency across the population of neurons as a function of distance from the best direction. In young monkeys, there was a slight increase in latency in A1 neurons with increasing distance from the best direction (gray circles). In contrast, for CL neurons there was a much greater increase in latency when stimuli far from the best direction were presented (gray squares). In contrast for both A1 and CL in aged animals (black symbols) the latency was largely invariant across spatial location in both A1 and CL, indicating that early inhibitory activity is normally spatially dependent in CL, and this is lost in aged animals.


Characterizing spatial tuning functions of neurons in the auditory cortex of young and aged monkeys: a new perspective on old data.

Engle JR, Recanzone GH - Front Aging Neurosci (2013)

Population first-spike latency. The first-spike latency at each location relative to the best direction is shown for young (gray) and aged (black) monkeys in A1 (circles) and CL (squares) in Panel (A). Aged monkeys had consistently shorter first-spike latencies than young animals. There was also no difference between A1 and CL in aged monkeys, but in young animals latency increased with distance from the best location. (B) Shows the regression between minimum latency and firing rate. There was a significant increase in latency with a decrease in firing rate in younger animals, but this correlation did not exist in aged animals.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3539457&req=5

Figure 8: Population first-spike latency. The first-spike latency at each location relative to the best direction is shown for young (gray) and aged (black) monkeys in A1 (circles) and CL (squares) in Panel (A). Aged monkeys had consistently shorter first-spike latencies than young animals. There was also no difference between A1 and CL in aged monkeys, but in young animals latency increased with distance from the best location. (B) Shows the regression between minimum latency and firing rate. There was a significant increase in latency with a decrease in firing rate in younger animals, but this correlation did not exist in aged animals.
Mentions: We also considered how first-spike latency was related to the spatial location of the stimulus. Figure 8A shows the minimum first-spike latency across the population of neurons as a function of distance from the best direction. In young monkeys, there was a slight increase in latency in A1 neurons with increasing distance from the best direction (gray circles). In contrast, for CL neurons there was a much greater increase in latency when stimuli far from the best direction were presented (gray squares). In contrast for both A1 and CL in aged animals (black symbols) the latency was largely invariant across spatial location in both A1 and CL, indicating that early inhibitory activity is normally spatially dependent in CL, and this is lost in aged animals.

Bottom Line: It is also possible that spatial tuning was decreased as a consequence of reduced inhibition at non-best locations.In this report we found that aged animals had greater activity throughout the response period, but primarily during the onset of the response.These results can be interpreted in the context of a failure of the timing and efficiency of feed-forward thalamo-cortical and cortico-cortical circuits in aged animals.

View Article: PubMed Central - PubMed

Affiliation: Department of Psychology and Center for Neuroscience, University of California at Davis Davis, CA, USA ; Evelyn F. McKnight Brain Institute and ARL Division of Neural Systems, Memory and Aging, University of Arizona Tucson, AZ, USA.

ABSTRACT
Age-related hearing deficits are a leading cause of disability among the aged. While some forms of hearing deficits are peripheral in origin, others are centrally mediated. One such deficit is the ability to localize sounds, a critical component for segregating different acoustic objects and events, which is dependent on the auditory cortex. Recent evidence indicates that in aged animals the normal sharpening of spatial tuning between neurons in primary auditory cortex to the caudal lateral field does not occur as it does in younger animals. As a decrease in inhibition with aging is common in the ascending auditory system, it is possible that this lack of spatial tuning sharpening is due to a decrease in inhibition at different periods within the response. It is also possible that spatial tuning was decreased as a consequence of reduced inhibition at non-best locations. In this report we found that aged animals had greater activity throughout the response period, but primarily during the onset of the response. This was most prominent at non-best directions, which is consistent with the hypothesis that inhibition is a primary mechanism for sharpening spatial tuning curves. We also noted that in aged animals the latency of the response was much shorter than in younger animals, which is consistent with a decrease in pre-onset inhibition. These results can be interpreted in the context of a failure of the timing and efficiency of feed-forward thalamo-cortical and cortico-cortical circuits in aged animals. Such a mechanism, if generalized across cortical areas, could play a major role in age-related cognitive decline.

No MeSH data available.


Related in: MedlinePlus