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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 spatial tuning index during different response periods. Panel (A) shows the RTI during the early, late, and off periods in A1 of young (gray) and aged (black) monkeys. There were differences found except during the off period. Panel (B) shows the results from CL neurons. Here, aged monkeys were more broadly spatial tuned during the early period (**p < 0.01).
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Figure 5: Population spatial tuning index during different response periods. Panel (A) shows the RTI during the early, late, and off periods in A1 of young (gray) and aged (black) monkeys. There were differences found except during the off period. Panel (B) shows the results from CL neurons. Here, aged monkeys were more broadly spatial tuned during the early period (**p < 0.01).

Mentions: We then analyzed the shape of the spatial tuning curves from each neuron with the RTI. The results of this analysis are shown in Figure 5. The RTI of neurons in A1 of young monkeys gradually changed across the early, late, and off response periods, F(2, 1275) = 131.01, p < 0.001. We found that this effect was driven by a significant increase (broadening) between the early and off, and the late and off response periods (Tukey Test, p < 0.001). The same effect was found for CL neurons, F(2, 1275) = 76.867, p < 0.001. We found that spatial tuning in CL neurons also became significantly broader between the early and off, and late and off response periods (Tukey Test, p < 0.001). These results suggest that the spatial tuning of A1 and CL neurons are more sharply tuned following stimulus onset, and gradually become broader over the stimulus period. The data from A1 neurons in aged monkeys followed a similar pattern. Spatial tuning was found to gradually increase across the early, late, and off response periods, F(2, 1275) = 22.52, p < 0.001. We found that the spatial tuning of A1 neurons became significantly broader between the early and off, and late and off response periods (Tukey Test, p < 0.001). A different pattern, however, was found in CL neurons of aged monkeys. Spatial tuning was found to be different across all response periods, F(2, 1275) = 13.61, p < 0.001. This time, however, we found that the spatial tuning of CL neurons in aged monkeys was significantly lower (sharper) during the late period than during the early and off periods (Tukey Test, p < 0.001). These results suggests that A1 neurons in aged monkeys follow a similar pattern of gradually becoming broadly tuned over the stimulus period; whereas, CL neurons in aged monkeys follow a refinement pattern that is different from A1 neurons.


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 spatial tuning index during different response periods. Panel (A) shows the RTI during the early, late, and off periods in A1 of young (gray) and aged (black) monkeys. There were differences found except during the off period. Panel (B) shows the results from CL neurons. Here, aged monkeys were more broadly spatial tuned during the early period (**p < 0.01).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 5: Population spatial tuning index during different response periods. Panel (A) shows the RTI during the early, late, and off periods in A1 of young (gray) and aged (black) monkeys. There were differences found except during the off period. Panel (B) shows the results from CL neurons. Here, aged monkeys were more broadly spatial tuned during the early period (**p < 0.01).
Mentions: We then analyzed the shape of the spatial tuning curves from each neuron with the RTI. The results of this analysis are shown in Figure 5. The RTI of neurons in A1 of young monkeys gradually changed across the early, late, and off response periods, F(2, 1275) = 131.01, p < 0.001. We found that this effect was driven by a significant increase (broadening) between the early and off, and the late and off response periods (Tukey Test, p < 0.001). The same effect was found for CL neurons, F(2, 1275) = 76.867, p < 0.001. We found that spatial tuning in CL neurons also became significantly broader between the early and off, and late and off response periods (Tukey Test, p < 0.001). These results suggest that the spatial tuning of A1 and CL neurons are more sharply tuned following stimulus onset, and gradually become broader over the stimulus period. The data from A1 neurons in aged monkeys followed a similar pattern. Spatial tuning was found to gradually increase across the early, late, and off response periods, F(2, 1275) = 22.52, p < 0.001. We found that the spatial tuning of A1 neurons became significantly broader between the early and off, and late and off response periods (Tukey Test, p < 0.001). A different pattern, however, was found in CL neurons of aged monkeys. Spatial tuning was found to be different across all response periods, F(2, 1275) = 13.61, p < 0.001. This time, however, we found that the spatial tuning of CL neurons in aged monkeys was significantly lower (sharper) during the late period than during the early and off periods (Tukey Test, p < 0.001). These results suggests that A1 neurons in aged monkeys follow a similar pattern of gradually becoming broadly tuned over the stimulus period; whereas, CL neurons in aged monkeys follow a refinement pattern that is different from A1 neurons.

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