scholarly journals Temporally Staggered Forelimb Stimulation Modulates Barrel Cortex Optical Intrinsic Signal Responses to Whisker Stimulation

2002 ◽  
Vol 88 (1) ◽  
pp. 422-437 ◽  
Author(s):  
Anne J. Blood ◽  
Nader Pouratian ◽  
Arthur W. Toga
Keyword(s):  
Response Time ◽  
Time Course ◽  
Barrel Cortex ◽  
Functional Neuroimaging ◽  
Stimulus Onset ◽  
Response Magnitude ◽  
Intrinsic Signal ◽  
Time To Peak ◽  
Optical Intrinsic Signal ◽  
Whisker Stimulation

Characterization of neurovascular relationships is critical to accurate interpretation of functional neuroimaging data. We have previously observed spatial uncoupling of optical intrinsic signal imaging (OIS) and evoked potential (EP) responses in rodent barrel cortex following simultaneous whisker and forelimb stimulation, leading to changes in OIS response magnitude. To further test the hypothesis that this uncoupling may have resulted from “passive” overspill of perfusion-related responses between functional regions, we conducted the present study using temporally staggered rather than simultaneous whisker and forelimb stimulation. This paradigm minimized overlap of neural responses in barrel cortex and forelimb primary somatosensory cortex (SI), while maintaining overlap of vascular response time courses between regions. When contrasted with responses to 1.5-s lone-whisker stimulation, staggered whisker and forelimb stimulation resulted in broadening of barrel cortex OIS response time course in the temporal direction of forelimb stimulation. OIS response peaks were also temporally shifted toward the forelimb stimulation period; time-to-peak was shorter (relative to whisker stimulus onset) when forelimb stimulation preceded whisker stimulation and longer when forelimb stimulation followed whisker stimulation. In contrast with OIS and EP magnitude decreases previously observed during simultaneous whisker/forelimb stimulation, barrel cortex OIS response magnitude increased during staggered stimulation and no detectable changes in underlying EP activity were observed. Spatial extent of barrel cortex OIS responses also increased during staggered stimulation. These findings provide further evidence for spatial uncoupling of OIS and EP responses, and emphasize the importance of temporal stimulus properties on the effects of this uncoupling. It is hypothesized that spatial uncoupling is a result of passive overspill of perfusion-related responses into regions distinct from those which are functionally active. It will be important to consider potential influences of this uncoupling when designing and interpreting functional imaging studies that use hemodynamic responses to infer underlying neural activity.

scholarly journals Stimulus Parameters Influence Characteristics of Optical Intrinsic Signal Responses in Somatosensory Cortex

1995 ◽  
Vol 15 (6) ◽  
pp. 1109-1120 ◽  
Author(s):  
Anne J. Blood ◽  
Sanjiv M. Narayan ◽  
Arthur W. Toga
Keyword(s):  
Barrel Cortex ◽  
Stimulus Frequency ◽  
Onset Time ◽  
Absolute Number ◽  
Regions Of Interest ◽  
Response Magnitude ◽  
Intrinsic Signal ◽  
Time To Peak ◽  
Optical Intrinsic Signal ◽  
Signal Response

Optical imaging of intrinsic signals was performed in the barrel cortex of the rat during whisker deflections of varying frequencies (1 to 20 Hz) and durations (0.1 to 5 s). A dose–response relationship was shown between these stimuli and the characteristics of the optically recorded intrinsic signal response. At constant frequencies, longer stimulus durations increased response magnitude, as defined by mean pixel value in statistically determined regions of interest. At constant durations, higher stimulus frequencies increased response magnitude. Response magnitude was also increased by greater numbers of deflections. When stimulus number was constant, there were no differences in response magnitude, regardless of stimulus frequency and duration. Spatial extent of responses, as defined by number of pixels in regions of interest, did not differ between stimulus frequencies, durations, or numbers. Comparison of the time to reach peak intrinsic signal response after stimulus onset (“time-to-peak”) suggested that higher frequencies were associated with faster time-to-peak. Registration of intrinsic signal responses with cytochrome oxidase-stained whisker barrels demonstrated that responses were located over the barrel corresponding to the stimulated whisker. In summary, we have shown that the absolute number of stimuli delivered to the system is, at least for short stimulus periods (≤5 s), a determining factor for the magnitude of these responses, whereas stimulus frequency appears to influence time-to-peak response.

scholarly journals Optical Intrinsic Signal Imaging Responses Are Modulated in Rodent Somatosensory Cortex during Simultaneous Whisker and Forelimb Stimulation

1998 ◽  
Vol 18 (9) ◽  
pp. 968-977 ◽  
Author(s):  
Anne J. Blood ◽  
Arthur W. Toga
Keyword(s):  
Evoked Potentials ◽  
Barrel Cortex ◽  
Response Magnitude ◽  
Response Patterns ◽  
Response Modulation ◽  
Intrinsic Signal ◽  
Optical Intrinsic Signal ◽  
Individual Trial ◽  
Cortical Responses ◽  
Different Response

Optical intrinsic signal imaging(OIS) was used to investigate physiologic interactions between spatially and functionally distinct cortical somatosensory systems. The OIS response magnitude was evaluated after simultaneous stimulation of single whiskers and forelimb digits. Whisker C1 was deflected at a frequency of 10 Hz for 2 seconds while low- or high-intensity vibratory stimuli were applied to forelimb digits. The OIS responses to simultaneous whisker and forelimb stimulation were compared with lone whisker stimulated controls. Overall, addition of a second stimulus caused decreases in barrel cortex response magnitude. Three different response patterns were detected within individual trial sets. Modulation of barrel cortex evoked potentials provided evidence that changes in OIS responses observed here may be partially influenced by vascular responses to changes in neuronal activity. However, OIS responses in the barrel region during lone forelimb stimulation that were unaccompanied by evoked potentials suggested the possibility of independent vascular dynamic influences on response modulation. This study demonstrates that cortical responses at the level of primary sensory processing may be significantly influenced by activity in adjacent regions. Furthermore, it reveals that vascular and neuronal characteristics of interregional modulation do not co-localize and may produce responses in which one component increases while the other decreases.

scholarly journals Varying the Degree of Single-Whisker Stimulation Differentially Affects Phases of Intrinsic Signals in Rat Barrel Cortex

1999 ◽  
Vol 81 (2) ◽  
pp. 692-701 ◽  
Author(s):  
Daniel B. Polley ◽  
Cynthia H. Chen-Bee ◽  
Ron D. Frostig
Keyword(s):  
Time Course ◽  
Barrel Cortex ◽  
Large Area ◽  
Intrinsic Signals ◽  
Intrinsic Signal ◽  
Point Spread ◽  
Signal Activity ◽  
Whisker Stimulation ◽  
Evoked Activity ◽  
Cortical Point

Varying the degree of single-whisker stimulation differentially affects phases of intrinsic signals in rat barrel cortex. . Neurophysiol. 81: 692–701, 1999. Using intrinsic signal optical imaging (ISI), we have shown previously that the point spread of evoked activity in the rat barrel cortex in response to single-whisker stimulation encompasses a surprisingly large area. Given that our typical stimulation consists of five deflections at 5 Hz, the large area of evoked activity might have resulted from repetitive stimulation. Thus in the present study, we use ISI through the thinned skull to determine whether decreasing the degree of single-whisker stimulation decreases the area of the cortical point spread. We additionally outline a protocol to quantify stimulus-related differences in the temporal characteristics of intrinsic signals at a fine spatial scale. In 10 adult rats, whisker C2 was stimulated randomly with either one or five deflections delivered in a rostral-to-caudal fashion. Each deflection consisted of a 0.5-mm displacement of the whisker as measured at the point of contact, 15 mm from the snout. The number of whisker deflections did not affect the area or peak magnitude of the cortical point spread based on the intrinsic signal activity occurring from 0.5 up to 1.5 s poststimulus onset. In contrast, the magnitude and time course of intrinsic signal activity collected after 1.5-s poststimulus onset did reflect the difference in the degree of stimulation. Thus decreasing the degree of stimulation differentially affected the early and late phases of the evoked intrinsic signal response. The implications of the present results are discussed in respect to probable differences in the signal source underlying the early versus later phases of evoked intrinsic signals.

Response of Anterior Parietal Cortex to Cutaneous Flutter Versus Vibration

1999 ◽  
Vol 82 (1) ◽  
pp. 16-33 ◽  
Author(s):  
M. Tommerdahl ◽  
K. A. Delemos ◽  
B. L. Whitsel ◽  
O. V. Favorov ◽  
C. B. Metz
Keyword(s):  
Firing Rate ◽  
Population Level ◽  
Early Response ◽  
Neuronal Population ◽  
Stimulus Onset ◽  
Skin Site ◽  
Intrinsic Signal ◽  
Optical Intrinsic Signal ◽  
Area 3B ◽  
Stimulation Of

The response of anesthetized squirrel monkey anterior parietal (SI) cortex to 25 or 200 Hz sinusoidal vertical skin displacement stimulation was studied using the method of optical intrinsic signal (OIS) imaging. Twenty-five-Hertz (“flutter”) stimulation of a discrete skin site on either the hindlimb or forelimb for 3–30 s evoked a prominent increase in absorbance within cytoarchitectonic areas 3b and 1 in the contralateral hemisphere. This response was confined to those area 3b/1 regions occupied by neurons with a receptive field (RF) that includes the stimulated skin site. In contrast, same-site 200-Hz stimulation (“vibration”) for 3–30 s evoked a decrease in absorbance in a much larger territory (most frequently involving areas 3b, 1, and area 3a, but in some subjects area 2 as well) than the region that undergoes an increase in absorbance during 25-Hz flutter stimulation. The increase in absorbance evoked by 25-Hz flutter developed quickly and remained relatively constant for as long as stimulation continued (stimulus duration never exceeded 30 s). At 1–3 s after stimulus onset, the response to 200-Hz stimulation, like the response to 25-Hz flutter, consisted of a localized increase in absorbance limited to the topographically appropriate region of area 3b and/or area 1. With continuing 200-Hz stimulation, however, the early response declined, and by 4–6 s after stimulus onset, it was replaced by a prominent and spatially extensive decrease in absorbance. The spike train responses of single quickly adapting (QA) neurons were recorded extracellularly during microelectrode penetrations that traverse the optically responding regions of areas 3b and 1. Onset of either 25- or 200-Hz stimulation at a site within the cutaneous RF of a QA neuron was accompanied by a substantial increase in mean spike firing rate. With continued 200-Hz stimulation, however, QA neuron mean firing rate declined rapidly (typically within 0.5–1.0 s) to a level below that recorded at the same time after onset of same-site 25-Hz stimulation. For some neurons, the mean firing rate after the initial 0.5–1 s of an exposure to 200-Hz stimulation of the RF decreased to a level below the level of background (“spontaneous”) activity. The decline in both the stimulus-evoked increases in absorbance in areas 3b/1 and spike discharge activity of area 3b/1 neurons within only a few seconds of the onset of 200-Hz skin stimulation raised the possibility that the predominant effect of continuous 200-Hz stimulation for >3 s is inhibition of area 3b/1 QA neurons. This possibility was evaluated at the neuronal population level by comparing the intrinsic signal evoked in areas 3b/1 by 25-Hz skin stimulation to the intrinsic signal evoked by a same-site skin stimulus containing both 25- and 200-Hz sinusoidal components (a “complex waveform stimulus”). Such experiments revealed that the increase in absorbance evoked in areas 3b/1 by a stimulus having both 25- and 200-Hz components was substantially smaller (especially at times >3 s after stimulus onset) than the increase in absorbance evoked by “pure” 25-Hz stimulation of the same skin site. It is concluded that within a brief time (within 1–3 s) after stimulus onset, 200-Hz skin stimulation elicits a powerful inhibitory action on area 3b/1 QA neurons. The findings appear generally consistent with the suggestion that the activity of neurons in cortical regions other than areas 3b and 1 play the leading role in the processing of high-frequency (≥200 Hz) vibrotactile stimuli.

scholarly journals Cortical Columnar Processing in the Rat Whisker-to-Barrel System

1999 ◽  
Vol 82 (4) ◽  
pp. 1808-1817 ◽  
Author(s):  
Joshua C. Brumberg ◽  
David J Pinto ◽  
Daniel J. Simons
Keyword(s):  
Time Course ◽  
Barrel Cortex ◽  
Random Noise ◽  
Stimulus Onset ◽  
Noise Stimulus ◽  
Thalamic Input ◽  
Afferent Information ◽  
Noise Vibration ◽  
Excitatory Responses ◽  
Local Circuits

Controlled whisker stimulation and single-unit recordings were used to elucidate response transformations that occur during the processing of tactile information from ventral posterior medial thalamus (VPM) through cortical columns in the rat whisker/barrel cortex. Whiskers were either deflected alone, using punctate ramp-and-hold stimuli, or in combination with a random noise vibration applied simultaneously to two or more neighboring whiskers. Quantitative data were obtained from five anatomically defined groups of neurons based on their being located in: VPM, layer IV barrels, layer IV septa, supragranular laminae, and infragranular laminae. Neurons in each of these populations displayed characteristic properties related to their response latency and time course, relative magnitudes of responses evoked by stimulus onset versus offset, strength of excitatory responses evoked by the noise stimulus, and/or the degree to which the noise stimulus, when applied to neighboring whiskers, suppressed or facilitated responses evoked by the columnar whisker. Results indicate that within layer IV itself there are at least two anatomically distinct networks, barrel and septum, that independently process afferent information, transforming thalamic input in similar but quantitatively distinguishable ways. Transformed signals are passed on to circuits in supragranular and infragranular laminae. In the case of supragranular neurons, evidence suggests that circuits there function in a qualitatively different fashion from those in layer IV, diminishing response differentials between weak and strong inputs, rather than enhancing them. Compared to layer IV, the greater heterogeneity of receptive field properties in nongranular layers suggests the existence of multiple, operationally distinct local circuits in the output layers of the cortical column.

scholarly journals Spatial Integration of Vascular Changes with Neural Activity in Mouse Cortex

2002 ◽  
Vol 22 (3) ◽  
pp. 353-360 ◽  
Author(s):  
Joseph P. Erinjeri ◽  
Thomas A. Woolsey
Keyword(s):  
Real Time ◽  
Barrel Cortex ◽  
Brain Regions ◽  
Histochemical Staining ◽  
Spatial Integration ◽  
Intrinsic Signals ◽  
Intrinsic Signal ◽  
Cortical Columns ◽  
Optical Intrinsic Signal ◽  
Mouse Cortex

The authors evaluated representations of discretely activated, neighboring brain regions using real-time optical intrinsic signals by transcranial imaging with 540-nm and 610-nm broadband illumination of the mouse barrel cortex. Iron filings were glued to two neighboring whiskers (C2 + D2) that were stimulated magnetically, singly and together. Real-time images were collected, averaged, and analyzed statistically. Postmortem filling of arteries with fluorescent beads was shown in relation to histochemical staining of barrels to accurately relate surface changes to functional cortical columns. Significant optical intrinsic signal changes are related to overlapping distributions of arterioles that feed the two separate areas. Activation of adjacent and interacting cortical columns leads not only to increased magnitude of vascular responses in those columns, but also to wider spatial extent of absorption changes occurring principally in areas of cortex fed by vessels upstream of the active cortex. The localization of changing hemoglobin absorption around upstream blood vessels and their vascular domains suggests that propagated vasodilation of upstream parent vessels is greater when vasodilatory signals from separate areas of active cortex converge on common arterioles that feed them.

Effects of prolonged light exposure, GABA, and glycine on horizontal cell responses in tiger salamander retina

1989 ◽  
Vol 61 (5) ◽  
pp. 1025-1035 ◽  
Author(s):  
X. L. Yang ◽  
S. M. Wu
Keyword(s):  
Response Time ◽  
Rise Time ◽  
Time Course ◽  
Light Exposure ◽  
Horizontal Cell ◽  
High Dose ◽  
Tiger Salamander ◽  
Gamma Aminobutyric Acid ◽  
Time To Peak ◽  
Cell Responses

1. The effects of prolonged light exposure, gamma-aminobutyric acid (GABA), and glycine on the horizontal cell (HC) light responses were studied in the superfused flat-mounted isolated retinas of the larval tiger salamander. 2. Under prolonged dark-adapted conditions, the time-to-peak of the HC light response was approximately 2-4 s, and after the termination of prolonged (6-8 min) light exposure, the time-to-peak became approximately 0.5-1 s. 3. This prolonged light-induced change in response rise time was not observed in either photoreceptors or bipolar cells, and thus the change in HC response rise time may occur postsynaptically in the HC membrane. 4. Application of 100 microM of GABA mimicked prolonged darkness and reversibly slowed down the HC response rise time, and application of 100 microM bicuculline mimicked prolonged light exposure and reversibly sped up the HC response rise time. 5. Glycine also slowed down the HC response rise course, but its effect was not observable until the concentration was raised to 1-3 mM. Strychnine did not exert any effect on HC responses when applied alone, but it could reverse the glycine actions. 6. The actions of glycine disappeared in the presence of bicuculline, indicating that the GABA and glycine pathways were probably not independent. Application of 5-10 mM glycine produced an increase of flow of preloaded 3H-GABA from the retina. 7. These results indicate that GABA may be the primary modulator that slows down the kinetics of the postsynaptic membrane proteins in the HCs. The extracellular concentration of GABA is probably high in prolonged darkness, and it is low after prolonged light exposure. Glycine, when applied at high dose, results in an increase of GABA release that slows down the HC response time course. 8. Prolonged darkness and light exposure appear to modulate the HC response in the time domain through GABA, and this change in HC response time course is probably responsible for shaping the bipolar cell responses and making the retinal signals more transient under light-adapted conditions.

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