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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

Firing rates as a function of stimulus location. Population firing rate curves relative to the best direction of each cell. (A–C) Show the absolute firing rate; (D–F) show rates normalized to the best direction of the young animals. Response profiles in the early (A,D), late (B,E), and off (C,F) periods are shown. Aged animals have a much greater driven firing rate than young animals (A–C). The difference in the shape of the tuning functions is minimal for A1 neurons (circles) except in the off period. However, the tuning functions are much sharper in young CL compared to aged CL (squares) across all three response periods. See Table 2 for SEMs.
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Figure 4: Firing rates as a function of stimulus location. Population firing rate curves relative to the best direction of each cell. (A–C) Show the absolute firing rate; (D–F) show rates normalized to the best direction of the young animals. Response profiles in the early (A,D), late (B,E), and off (C,F) periods are shown. Aged animals have a much greater driven firing rate than young animals (A–C). The difference in the shape of the tuning functions is minimal for A1 neurons (circles) except in the off period. However, the tuning functions are much sharper in young CL compared to aged CL (squares) across all three response periods. See Table 2 for SEMs.

Mentions: The previous analyses revealed that there is a higher firing rate in neurons from aged animals compared to those from young animals and that the response becomes less sustained as the stimulus moves away from the best direction. To provide an additional layer of quantification, we examined the driven response during the early, late, and off response periods as a function of degrees from the best direction in A1 and CL of young and aged monkeys. In order to examine how the overall firing rate influenced spatial tuning during the three different response periods, the average neuronal response was calculated by averaging the driven firing rate minus the spontaneous rate for all neurons recorded at each direction. Figure 4 illustrates the average firing rate spatial tuning curves during the early, late, and off response periods.


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)

Firing rates as a function of stimulus location. Population firing rate curves relative to the best direction of each cell. (A–C) Show the absolute firing rate; (D–F) show rates normalized to the best direction of the young animals. Response profiles in the early (A,D), late (B,E), and off (C,F) periods are shown. Aged animals have a much greater driven firing rate than young animals (A–C). The difference in the shape of the tuning functions is minimal for A1 neurons (circles) except in the off period. However, the tuning functions are much sharper in young CL compared to aged CL (squares) across all three response periods. See Table 2 for SEMs.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 4: Firing rates as a function of stimulus location. Population firing rate curves relative to the best direction of each cell. (A–C) Show the absolute firing rate; (D–F) show rates normalized to the best direction of the young animals. Response profiles in the early (A,D), late (B,E), and off (C,F) periods are shown. Aged animals have a much greater driven firing rate than young animals (A–C). The difference in the shape of the tuning functions is minimal for A1 neurons (circles) except in the off period. However, the tuning functions are much sharper in young CL compared to aged CL (squares) across all three response periods. See Table 2 for SEMs.
Mentions: The previous analyses revealed that there is a higher firing rate in neurons from aged animals compared to those from young animals and that the response becomes less sustained as the stimulus moves away from the best direction. To provide an additional layer of quantification, we examined the driven response during the early, late, and off response periods as a function of degrees from the best direction in A1 and CL of young and aged monkeys. In order to examine how the overall firing rate influenced spatial tuning during the three different response periods, the average neuronal response was calculated by averaging the driven firing rate minus the spontaneous rate for all neurons recorded at each direction. Figure 4 illustrates the average firing rate spatial tuning curves during the early, late, and off response periods.

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