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M L Sutter

Publications and source records attributed to M L Sutter.

5 recordsLinked to original sources
PubMed1992

Functional topography of cat primary auditory cortex: representation of tone intensity.

The neuronal response to tones as a function of intensity was topographically studied with multiple-unit recordings in the primary auditory cortex (AI) of barbiturate-anesthetized cats. The spatial distribution of the characteristics of rate/level functions was determined in each of three intensely studied cases and their relationship to the distribution of spectral parameters (sharpness of tuning and responses to broadband transients) in the same animals was determined. The growth of the high-intensity portion of rate/level functions was estimated by linear regression. Locations with monotonically growing high-intensity portions were spatially segregated from locations with nonmonotonic rate/level functions. Two noncontiguous areas with a high degree of nonmonotonicity were observed. One was located at the dorsoventral center of AI, and a second in the dorsal third of AI. The more ventral aggregate of high nonmonotonicity coincided with the region of sharp frequency tuning. The stimulus levels that produced the highest firing rate (strongest response level, SRL) at any sampled location ranged from 10 to 80 dB sound pressure level (SPL). Several spatial aggregates with either high or low SRLs were observed in AI. The region of sharpest tuning was always associated with a region of low SRLs. The response threshold to contralateral tones at the characteristic frequency (CF) ranged from -10 dB SPL to 85 dB SPL with the majority between 0 and 40 dB SPL. The spatial distribution of response thresholds indicated several segregated areas containing clusters with either higher or lower response thresholds. The correlation of response threshold with integrated bandwidth and transient responses was only weak. Low- and high-intensity tones of the same frequency are represented at different locations in AI as judged by the amount of evoked neuronal activity and are largely independent of the frequency organization. The spatial distribution of locations with high monotonicity and low strongest response levels were aligned with the organization of the integrated excitatory bandwidth and covaried with the response strength to broadband stimuli.

Acoustic Stimulation↗
PubMed1992

Topography of excitatory bandwidth in cat primary auditory cortex: single-neuron versus multiple-neuron recordings.

1. The spatial distribution of the sharpness of tuning of single neurons along the dorsoventral extent of primary auditory cortex (AI) was studied. A sharpness of tuning gradient was initially obtained with multiple-unit recordings, and in combination with the cochleotopic organization, served as a frame of reference for the locations of single neurons. The frequency selectivity or "integrated excitatory bandwidth" of multiple units varied systematically along the dorsoventral extent of AI. The most sharply tuned unit clusters were found at the approximate center of the dorsoventral extent. A gradual broadening of the integrated excitatory bandwidth in both dorsal and ventral directions was consistently seen. 2. The multiple-unit measures of the bandwidth 10 (BW10) and 40 dB (BW40) above minimum threshold, pooled across several animals and expressed in octaves, were similar to those described within individual cases in cats. As in the individual animals, the bandwidth maps were V shaped with minima located at the approximate center of the dorsal-ventral extent of AI. The location of the minimum in the multiple-unit bandwidth map (i.e., the most sharply tuned area) was used as a reference point to pool single-neuron data across animals. 3. For single neurons, the dorsal half of the BW40 distribution showed a gradient paralleling that found for multiple units. For both single and multiple units, the average excitatory bandwidth increased at a rate of approximately 0.27 octaves/mm from the center of AI toward the dorsal fringe. Differing from the dorsal half of AI, the ventral half of AI showed no clear BW40 gradient for single units along its dorsoventral extent. At 40 dB above minimum threshold, most ventral neurons encountered were sharply tuned. By contrast, the multiple-unit BW40 showed a gradient similar to the dorsal half with 0.23 octaves/mm increasing from the center toward the ventral border of AI. 4. For single neurons, BW10 showed no clear systematic spatial distribution in AI. Neither the dorsal nor the ventral gradient was significantly different from zero slope, although the dorsal half showed a trend toward increasing BW10s. Contrasting single neurons, both dorsal and ventral halves of AI showed BW10 slopes for multiple units confirming a V-shaped map of the integrated excitatory bandwidth within the dorsoventral extent of AI. 5. On the basis of the distribution of the integrated (multiple-unit) excitatory bandwidth, AI was parceled into three regions: the dorsal gradient, the ventral gradient, and the central, narrowly tuned area.(ABSTRACT TRUNCATED AT 400 WORDS)

Acoustic Stimulation↗
PubMed1991

Physiology and topography of neurons with multipeaked tuning curves in cat primary auditory cortex.

1. The physiology and topography of single neuron responses along the isofrequency domain of the middle- and high-frequency portions [characteristic frequencies (CFs) greater than 4 kHz] of the primary auditory cortex (AI) were investigated in the barbiturate-anesthetized cat. Single neurons were recorded at several locations along the extent of isofrequency contours, defined from initial multiple-unit mapping. For each neuron a high-resolution excitatory tuning curve was determined, and for some neurons high-resolution two-tone tuning curves were recorded to measure inhibitory/suppressive areas. 2. A physiologically distinct population of neurons was found in the dorsal part of cat AI. These neurons exhibited two or three distinct excitatory frequency ranges, whereas most neurons in AI responded with excitation to a single narrow frequency range. These were called multipeaked neurons because of the shape of their tuning curves. At frequencies between the excitatory regions, the multipeaked neurons were inhibited or unresponsive. 3. Multipeaked neurons exhibited several distinct threshold minima in their frequency tuning curves. Most of the multipeaked neurons (88%) displayed two frequency minima, whereas the rest exhibited three minima. 4. The frequency separation between threshold minima was less than 1 octave in 71% of the double-peaked neurons recorded. Occasionally, the frequency peaks of these neurons closely corresponded to a response to second and third harmonics without a response to the fundamental frequency. 5. Multipeaked neurons exhibited a wide range of total bandwidths (highest excitatory frequency minus lowest excitatory frequency expressed in octaves). Bandwidths of the isolated peaks within the same neuron were also quite variable. 6. Response latencies to tones with frequencies within each peak of a multipeaked neuron could vary considerably. In 71% (17) of the neurons, tones corresponding to the high-frequency peak (CFh) elicited a longer response latency (greater than 4 ms) than those corresponding to the low-frequency peak (CF1). 7. Inhibitory/suppressive bands, as demonstrated with a two-tone paradigm, were often present between the peaks. Typically, neurons with excitatory peaks of similar response latencies showed an inhibitory band located between the peaks. 8. Ninety percent of the topographically localized multipeaked neurons were in the dorsal part of AI (greater than 1 mm dorsal to the maximum in the sharpness-of-tuning map). Although these neurons were restricted to dorsal AI, only 35% of neurons in this region were multipeaked. 9. Multipeaked neurons could show decreased response latencies and thresholds to two-tone combinations.(ABSTRACT TRUNCATED AT 400 WORDS)

Acoustic Stimulation↗
PubMed1982

An interactive clinical data system.

A clinical data system is under development at the Upjohn Company that will reduce the time lag from patient visit to data availability, data entry errors, and the amount of training required for system use. The system design allows generality for both the study monitor and the biostatistician, editing of the data before entry, simplified forms design, direct entry of textual responses without coding, and a reduced need for special programs. Interactive subsystems allow a user to describe a study to the system, generate tailor-made entry/edit programs for each study, undate the date base, and produce ad hoc reports. The system is being implemented on top of a data base management system and runs on an IBM 370/148 under VM/CMS.

Clinical Trials as Topic↗