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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

Temporal response profiles of neuronal responses. Recorded neuronal responses varied along a continuum from early phasic (top), tonic (middle), to the late period only (bottom).
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Figure 1: Temporal response profiles of neuronal responses. Recorded neuronal responses varied along a continuum from early phasic (top), tonic (middle), to the late period only (bottom).

Mentions: Using standard single-unit recording techniques, we recorded the neuronal activity elicited by broadband noise bursts of 788 single neurons in auditory cortical areas A1 and CL in both young and aged alert monkeys (Table 1). Figure 1 shows five representative examples of the types of responses we encountered in both young and aged animals. We encountered neurons with a short duration onset response, those with a smaller or even absent onset response but a clear tonic response throughout the stimulus presentation, and those that only fired during the last part of the stimulus. This continuum is represented down each column of Figure 1, and as described previously in young animals in A1, forms a relatively uniform distribution (Recanzone, 2000).


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)

Temporal response profiles of neuronal responses. Recorded neuronal responses varied along a continuum from early phasic (top), tonic (middle), to the late period only (bottom).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 1: Temporal response profiles of neuronal responses. Recorded neuronal responses varied along a continuum from early phasic (top), tonic (middle), to the late period only (bottom).
Mentions: Using standard single-unit recording techniques, we recorded the neuronal activity elicited by broadband noise bursts of 788 single neurons in auditory cortical areas A1 and CL in both young and aged alert monkeys (Table 1). Figure 1 shows five representative examples of the types of responses we encountered in both young and aged animals. We encountered neurons with a short duration onset response, those with a smaller or even absent onset response but a clear tonic response throughout the stimulus presentation, and those that only fired during the last part of the stimulus. This continuum is represented down each column of Figure 1, and as described previously in young animals in A1, forms a relatively uniform distribution (Recanzone, 2000).

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