scholarly journals Stimulus-specific adaptation in auditory thalamus of young and aged awake rats

2013 ◽  
Vol 110 (8) ◽  
pp. 1892-1902 ◽  
Author(s):  
Ben D. Richardson ◽  
Kenneth E. Hancock ◽  
Donald M. Caspary
Keyword(s):  
Young Adult ◽  
Auditory Cortex ◽  
Brown Norway ◽  
Oddball Paradigm ◽  
Adult Rats ◽  
Specific Adaptation ◽  
Auditory Thalamus ◽  
Gating Mechanism ◽  
Medial Geniculate ◽  
Awake Rats

Novel stimulus detection by single neurons in the auditory system, known as stimulus-specific adaptation (SSA), appears to function as a real-time filtering/gating mechanism in processing acoustic information. Particular stimulus paradigms allowing for quantification of a neuron's ability to detect novel or deviant stimuli have been used to examine SSA in the inferior colliculus, medial geniculate body (MGB), and auditory cortex of anesthetized rodents. However, the study of SSA in awake animals is limited to auditory cortex. The present study used individually advanceable tetrodes to record single-unit responses from auditory thalamus (MGB) of awake young adult and aged Fischer Brown Norway (FBN) rats to 1) examine the presence of SSA in the MGB of awake rats and 2) determine whether SSA is altered by aging in MGB. MGB single units in awake FBN rats displayed SSA in response to two stimulus paradigms: the oddball paradigm and a random blocked/interleaved presentation of a set of frequencies. SSA levels were modestly, but nonsignificantly, increased in the nonlemniscal regions of the MGB and at lower stimulus intensities, where 27 of 57 (47%) young adult MGB units displayed SSA. The present findings provide the initial description of SSA in the MGB of awake rats and support SSA as being qualitatively independent of arousal level or anesthetized state. Finally, contrary to previous studies in auditory cortex of anesthetized rats, MGB units in aged rats showed SSA levels indistinguishable from SSA levels in young adult rats, suggesting that SSA in MGB was not impacted by aging in an awake preparation.

scholarly journals Differential effects of targeted tongue exercise and treadmill running on aging tongue muscle structure and contractile properties

2013 ◽  
Vol 114 (4) ◽  
pp. 472-481 ◽  
Author(s):  
Heidi Kletzien ◽  
John A. Russell ◽  
Glen E. Leverson ◽  
Nadine P. Connor
Keyword(s):  
Young Adult ◽  
Exercise Group ◽  
Contractile Properties ◽  
Treadmill Running ◽  
Brown Norway ◽  
Middle Aged ◽  
Adult Rats ◽  
Tongue Muscle ◽  
Muscle Structure ◽  
Old Rats

Age-associated changes in tongue muscle structure and strength may contribute to dysphagia in elderly people. Tongue exercise is a current treatment option. We hypothesized that targeted tongue exercise and nontargeted exercise that activates tongue muscles as a consequence of increased respiratory drive, such as treadmill running, are associated with different patterns of tongue muscle contraction and genioglossus (GG) muscle biochemistry. Thirty-one young adult, 34 middle-aged, and 37 old Fischer 344/Brown Norway rats received either targeted tongue exercise, treadmill running, or no exercise (5 days/wk for 8 wk). Protrusive tongue muscle contractile properties and myosin heavy chain (MHC) composition in the GG were examined at the end of 8 wk across groups. Significant age effects were found for maximal twitch and tetanic tension (greatest in young adult rats), MHCIIb (highest proportion in young adult rats), MHCIIx (highest proportion in middle-aged and old rats), and MHCI (highest proportion in old rats). The targeted tongue exercise group had the greatest maximal twitch tension and the highest proportion of MHCI. The treadmill running group had the shortest half-decay time, the lowest proportion of MHCIIa, and the highest proportion of MHCIIb. Fatigue was significantly less in the young adult treadmill running group and the old targeted tongue exercise group than in other groups. Thus, tongue muscle structure and contractile properties were affected by both targeted tongue exercise and treadmill running, but in different ways. Studies geared toward optimizing dose and manner of providing targeted and generalized tongue exercise may lead to alternative tongue exercise delivery strategies.

Modulatory Effect of Cortical Activation on the Lemniscal Auditory Thalamus of the Guinea Pig

2002 ◽  
Vol 88 (2) ◽  
pp. 1040-1050 ◽  
Author(s):  
Jufang He ◽  
Yan-Qin Yu ◽  
Ying Xiong ◽  
Tsutomu Hashikawa ◽  
Ying-Shing Chan
Keyword(s):  
Guinea Pig ◽  
Auditory Cortex ◽  
Firing Pattern ◽  
Inhibitory Effect ◽  
Electrical Activation ◽  
Facilitatory Effect ◽  
Thalamic Neurons ◽  
Auditory Thalamus ◽  
Medial Geniculate ◽  
Corticofugal Modulation

In the present study, we investigated the point-to-point modulatory effects from the auditory cortex to the thalamus in the guinea pig. Corticofugal modulation on thalamic neurons was studied by electrical activation of the auditory cortex. The modulation effect was sampled along the frontal or sagittal planes of the auditory thalamus, focusing on the ventral division (MGv) of the medial geniculate body (MGB). Electrical activation was targeted at the anterior and dorsocaudal auditory fields, to which the MGv projects and from which it assumptively receives reciprocal projections. Of the 101 MGv neurons examined by activation of the auditory cortex through passing pulse trains of 100–200 μA current into one after another of the three implanted electrodes (101 neurons × 3 stimulation sites = 303 cases), 208 cases showed a facilitatory effect, 85 showed no effect, and only 10 cases (7 neurons) showed an inhibitory effect. Among the cases of facilitation, 63 cases showed a facilitatory effect >100%, and 145 cases showed a facilitatory effect from 20–100%. The corticofugal modulatory effect on the MGv of the guinea pig showed a widespread, strong facilitatory effect and very little inhibitory effect. The MGv neurons showed the greatest facilitations to stimulation by the cortical sites, with the closest correspondence in BF. Six of seven neurons showed an elevation of the rate-frequency functions when the auditory cortex was activated. The comparative results of the corticofugal modulatory effects on the MGv of the guinea pig and the cat, together with anatomical findings, hint that the strong facilitatory effect is generated through the strong corticothalamic direct connection and that the weak inhibitory effect might be mainly generated via the interneurons of the MGv. The temporal firing pattern of neuronal response to auditory stimulus was also modulated by cortical stimulation. The mean first-spike latency increased significantly from 15.7 ± 5.3 ms with only noise-burst stimulus to 18.3 ± 4.9 ms ( n = 5, P < 0.01, paired t-test), while the auditory cortex was activated with a train of 10 pulses. Taking these results together with those of previous experiments conducted on the cat, we speculate that the relatively weaker inhibitory effect compared with that in the cat could be due to the smaller number of interneurons in the guinea pig MGB. The corticofugal modulation of the firing pattern of the thalamic neurons might enable single neurons to encode more auditory information using not only the firing rate but also the firing pattern.

scholarly journals Increased myogenic repressor Id mRNA and protein levels in hindlimb muscles of aged rats

2002 ◽  
Vol 282 (2) ◽  
pp. R411-R422 ◽  
Author(s):  
Stephen E. Alway ◽  
Hans Degens ◽  
Dawn A. Lowe ◽  
Gururaj Krishnamurthy
Keyword(s):  
Young Adult ◽  
Mrna Level ◽  
Brown Norway ◽  
Mrna Levels ◽  
Aged Rats ◽  
Adult Rats ◽  
Protein Levels ◽  
Fast And Slow Muscles ◽  
Hindlimb Muscles ◽  
Gastrocnemius Muscles

The objective of this study was to determine if levels of repressors to myogenic regulatory factors (MRFs) differ between muscles from young adult and aged animals. Total RNA from plantaris, gastrocnemius, and soleus muscles of Fischer 344 × Brown Norway rats aged 9 mo (young adult, n = 10) and 37 mo (aged, n = 10) was reverse transcribed and then amplified by PCR. To obtain a semiquantitative measure of the mRNA levels, PCR signals were normalized to cyclophilin or 18S signals from the corresponding reverse transcription product. Normalization to cyclophilin and 18S gave similar results. The mRNA levels of MyoD and myogenin were ∼275–650% ( P < 0.001) and ∼500–1,100% ( P < 0.001) greater, respectively, in muscles from aged compared with young adults. In contrast, the protein levels were lower in plantaris and gastrocnemius muscles and similar in the soleus muscle of aged vs. young adult rats. Id repressor mRNA levels were ∼300–900% greater in fast and slow muscles of aged animals ( P ≤ 0.02), and Mist 1 mRNA was ∼50% greater in the plantaris and gastrocnemius muscles ( P< 0.01). The mRNA level of Twist mRNA was not significantly affected by aging. Id-1, Id-2, and Id-3 protein levels were ∼17–740% greater ( P < 0.05) in hindlimb muscles of aged rats compared with young adult rats. The elevated levels of Id mRNA and protein suggest that MRF repressors may play a role in gene regulation of fast and slow muscles in aged rats.

scholarly journals Aging Effects on the Limits and Stability of Long-Term Synaptic Potentiation and Depression in Rat Hippocampal Area CA1

2007 ◽  
Vol 98 (2) ◽  
pp. 594-601 ◽  
Author(s):  
Ashok Kumar ◽  
Jeffrey S. Thinschmidt ◽  
Thomas C. Foster ◽  
Michael A. King
Keyword(s):  
Synaptic Plasticity ◽  
Young Adult ◽  
Hippocampal Slices ◽  
Long Term Potentiation ◽  
Brown Norway ◽  
Aging Effects ◽  
Adult Rats ◽  
Age Related ◽  
Significant Difference

Altered hippocampal synaptic plasticity may underlie age-related memory impairment. In acute hippocampal slices from aged (22–24 mo) and young adult (1–12 mo) male Brown Norway rats, extracellular excitatory postsynaptic field potentials were recorded in CA1 stratum radiatum evoked by Schaffer collateral stimulation. We used enhanced Ca2+ to Mg2+ ratio and paired-pulse stimulation protocol to induce maximum changes in the synaptic plasticity. Six episodes of theta-burst stimulation (TBS) or nine episodes of paired low-frequency stimulation (pLFS) were used to generate asymptotic long-term potentiation (LTP) and long-term depression (LTD), respectively. In addition, long-term depotentiation (LTdeP) or de-depression (LTdeD) from maximal LTP and LTD were examined using two episodes of pLFS or TBS. Multiple episodes of TBS or pLFS produced significant LTP or LTD in aged and young adult rats; this was not different between age groups. Moreover, there was no significant difference in the amount of LTdeP or LTdeD between aged and young adult rats. Our results show no age differences in the asymptotic magnitude of LTP or LTD, rate of synaptic modifications, development rates, reversal, or decay after postconditioning. Thus impairment of the basic synaptic mechanisms responsible for expression of these forms of plasticity is not likely to account for decline in memory function within this age range.

scholarly journals Multiparametric Auditory Receptive Field Organization Across Five Cortical Fields in the Albino Rat

2007 ◽  
Vol 97 (5) ◽  
pp. 3621-3638 ◽  
Author(s):  
Daniel B. Polley ◽  
Heather L. Read ◽  
Douglas A. Storace ◽  
Michael M. Merzenich
Keyword(s):  
Receptive Field ◽  
Auditory Cortex ◽  
Relative Position ◽  
Adult Rats ◽  
Albino Rat ◽  
Physical Scale ◽  
Medial Geniculate ◽  
Field Organization ◽  
Receptive Field Organization ◽  
Auditory Field

The auditory cortex of the rat is becoming an increasingly popular model system for studies of experience-dependent receptive field plasticity. However, the relative position of various fields within the auditory core and the receptive field organization within each field have yet to be fully described in the normative case. In this study, the macro- and micro-organizational features of the auditory cortex were studied in pentobarbital-anesthetized adult rats with a combination of physiological and anatomical methods. Dense microelectrode mapping procedures were used to identify the relative position of five tonotopically organized fields within the auditory core: primary auditory cortex (AI), the posterior auditory field (PAF), the anterior auditory field (AAF), the ventral auditory field (VAF), and the suprarhinal auditory field (SRAF). AI and AAF both featured short-latency, sharply tuned responses with predominantly monotonic intensity-response functions. SRAF and PAF were both characterized by longer-latency, broadly tuned responses. VAF directly abutted the ventral boundary of AI but was almost exclusively composed of low-threshold nonmonotonic intensity-tuned responses. Dual injection of retrograde tracers into AI and VAF was used to demonstrate that the sources of thalamic input from the medial geniculate body to each area were essentially nonoverlapping. An analysis of receptive field parameters beyond characteristic frequency revealed independent spatially ordered representations for features related to spectral tuning, intensity tuning, and onset response properties in AI, AAF, VAF, and SRAF. These data demonstrate that despite its greatly reduced physical scale, the rat auditory cortex features a surprising degree of organizational complexity and detail.

Myogenic regulatory factors during regeneration of skeletal muscle in young, adult, and old rats

1997 ◽  
Vol 83 (4) ◽  
pp. 1270-1275 ◽  
Author(s):  
Daniel R. Marsh ◽  
David S. Criswell ◽  
James A. Carson ◽  
Frank W. Booth
Keyword(s):  
Skeletal Muscle ◽  
Young Adult ◽  
Muscle Regeneration ◽  
Tibialis Anterior Muscle ◽  
Brown Norway ◽  
Mrna Levels ◽  
Myogenic Regulatory Factors ◽  
Adult Rats ◽  
Regulatory Factors ◽  
Old Rats

Marsh, Daniel R., David S. Criswell, James A. Carson, and Frank W. Booth. Myogenic regulatory factors during regeneration of skeletal muscle in young, adult, and old rats. J. Appl. Physiol. 83(4): 1270–1275, 1997.—Myogenic factor mRNA expression was examined during muscle regeneration after bupivacaine injection in Fischer 344/Brown Norway F1 rats aged 3, 18, and 31 mo of age (young, adult, and old, respectively). Mass of the tibialis anterior muscle in the young rats had recovered to control values by 21 days postbupivacaine injection but in adult and old rats remained 40% less than that of contralateral controls at 21 and 28 days of recovery. During muscle regeneration, myogenin mRNA was significantly increased in muscles of young, adult, and old rats 5 days after bupivacaine injection. Subsequently, myogenin mRNA levels in young rat muscle decreased to postinjection control values by day 21 but did not return to control values in 28-day regenerating muscles of adult and old rats. The expression of MyoD mRNA was also increased in muscles at day 5 of regeneration in young, adult, and old rats, decreased to control levels by day 14 in young and adult rats, and remained elevated in the old rats for 28 days. In summary, either a diminished ability to downregulate myogenin and MyoD mRNAs in regenerating muscle occurs in old rat muscles, or the continuing myogenic effort includes elevated expression of these mRNAs.

Affects of Aging on Receptive Fields in Rat Primary Auditory Cortex Layer V Neurons

2005 ◽  
Vol 94 (4) ◽  
pp. 2738-2747 ◽  
Author(s):  
Jeremy G. Turner ◽  
Larry F. Hughes ◽  
Donald M. Caspary
Keyword(s):  
Receptive Field ◽  
Auditory Cortex ◽  
Receptive Fields ◽  
Primary Auditory Cortex ◽  
Brown Norway ◽  
Aged Rats ◽  
Adult Rats ◽  
Gabaergic Neurotransmission ◽  
Layer V

Advanced age is commonly associated with progressive cochlear pathology and central auditory deficits, collectively known as presbycusis. The present study examined central correlates of presbycusis by measuring response properties of primary auditory cortex (AI) layer V neurons in the Fischer Brown Norway rat model. Layer V neurons represent the major output of AI to other cortical and subcortical regions (primarily the inferior colliculus). In vivo single-unit extracellular recordings were obtained from 114 neurons in aged animals (29–33 mo) and compared with 105 layer V neurons in young-adult rats (4–6 mo). Three consecutive repetitions of a pure-tone receptive field map were run for each neuron. Age was associated with fewer neurons exhibiting classic V/U-shaped receptive fields and a greater percentage of neurons with more Complex receptive fields. Receptive fields from neurons in aged rats were also less reliable on successive repetitions of the same stimulus set. Aging was also associated with less firing during the stimulus in V/U-shaped receptive field neurons and more firing during the stimulus in Complex neurons, which were generally associated with inhibited firing in young controls. Finally, neurons in aged rats with Complex receptive fields were more easily driven by current pulses delivered to the soma. Collectively, these findings provide support for the notion that age is associated with diminished signal-to-noise coding by AI layer V neurons and are consistent with other research suggesting that GABAergic neurotransmission in AI may be compromised by aging.

scholarly journals Effects of Cortical Cooling on Sound Processing in Auditory Cortex and Thalamus of Awake Marmosets

2022 ◽  
Vol 15 ◽  
Author(s):  
Marcus Jeschke ◽  
Frank W. Ohl ◽  
Xiaoqin Wang
Keyword(s):  
Auditory Cortex ◽  
Cortical Neurons ◽  
Medial Geniculate Body ◽  
Spatial Location ◽  
Auditory Thalamus ◽  
Cortical Cooling ◽  
Medial Geniculate ◽  
Cortical Temperature ◽  
Corticofugal Feedback ◽  
Future Work

The auditory thalamus is the central nexus of bottom-up connections from the inferior colliculus and top-down connections from auditory cortical areas. While considerable efforts have been made to investigate feedforward processing of sounds in the auditory thalamus (medial geniculate body, MGB) of non-human primates, little is known about the role of corticofugal feedback in the MGB of awake non-human primates. Therefore, we developed a small, repositionable cooling probe to manipulate corticofugal feedback and studied neural responses in both auditory cortex and thalamus to sounds under conditions of normal and reduced cortical temperature. Cooling-induced increases in the width of extracellularly recorded spikes in auditory cortex were observed over the distance of several hundred micrometers away from the cooling probe. Cortical neurons displayed reduction in both spontaneous and stimulus driven firing rates with decreased cortical temperatures. In thalamus, cortical cooling led to increased spontaneous firing and either increased or decreased stimulus driven activity. Furthermore, response tuning to modulation frequencies of temporally modulated sounds and spatial tuning to sound source location could be altered (increased or decreased) by cortical cooling. Specifically, best modulation frequencies of individual MGB neurons could shift either toward higher or lower frequencies based on the vector strength or the firing rate. The tuning of MGB neurons for spatial location could both sharpen or widen. Elevation preference could shift toward higher or lower elevations and azimuth tuning could move toward ipsilateral or contralateral locations. Such bidirectional changes were observed in many parameters which suggests that the auditory thalamus acts as a filter that could be adjusted according to behaviorally driven signals from auditory cortex. Future work will have to delineate the circuit elements responsible for the observed effects.

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