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J B Preston

Publications and source records attributed to J B Preston.

At least 19 recordsLinked to original sources
PubMed1994

Interconnections between the prefrontal cortex and the premotor areas in the frontal lobe.

We examined interconnections between a portion of the prefrontal cortex and the premotor areas in the frontal lobe to provide insights into the routes by which the prefrontal cortex gains access to the primary motor cortex and the central control of movement. We placed multiple injections of one retrograde tracer in the arm area of the primary motor cortex to define the premotor areas in the frontal lobe. Then, in the same animal, we placed multiple injections of another retrograde tracer in and around the principal sulcus (Walker's area 46). This double labeling strategy enabled us to determine which premotor areas are interconnected with the prefrontal cortex. There are three major results of this study. First, we found that five of the six premotor areas in the frontal lobe are interconnected with the dorsolateral prefrontal cortex. Second, the major site for interactions between the prefrontal cortex and the premotor areas is the ventral premotor area. Third, the prefrontal cortex is interconnected with only a portion of the arm representation in three premotor areas (supplementary motor area, the caudal cingulate motor area on the ventral bank of the cingulate sulcus, and the dorsal premotor area), whereas it is interconnected with the entire arm representation in the ventral premotor area and the rostral cingulate motor area. These observations indicate that the output of the prefrontal cortex targets specific premotor areas and even subregions within individual premotor areas.

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PubMed1991

The origin of thalamic inputs to the "hand" representation in the primary motor cortex.

We used retrograde transport of WGA-HRP to examine the origin of thalamic inputs to the "hand" representation in the primary motor cortex of macaques (Macaca nemestrina). Injections were placed in either the crest of the precentral gyrus or the rostral bank of the central sulcus. The sites for injection in the sulcus were determined by using intracortical stimulation to map the location of hand representation. We found that the precentral gyrus and central sulcus receive their predominant input from different subdivisions of the ventrolateral thalamus. Ventralis posterior lateralis pars oralis (VPLo) provides the most substantial input to a portion of the hand representation on the gyrus. In contrast, Ventralis lateralis pars oralis (VLo) provides the most substantial input to a portion of the hand representation in the sulcus. Prior studies have shown that VPLo is a major site of termination of cerebellar efferents and that VLo is a major site of termination of pallidal efferents. Thus, our results indicate that both the basal ganglia and the cerebellum "directly" influence the "hand" representation of the primary motor cortex.

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PubMed1976

Classification and response characteristics of muscle spindle afferents in the primate.

A study was made of the response characteristics of spindle afferents in the baboon soleus muscle. Afferents were isolated from the dorsal roots, their conduction velocities were determined, and their responses were recorded to muscle stretch at rates of 2.5-45 mm/s and amplitudes of 2-10 mm. Spindle afferents could be classified as primary or secondary on the basis of two criteria. The first criterion was conduction velocity. The conduction velocity histogram was bimodal, with peaks at about 45 and 80 m/s and an intermediate region from 55 to 70 m/s. The second criterion was the pattern of adaptation following the peak of ramp stretch. This latter criterion has the advantage of allowing units with intermediate conduction velocities also to be confidently classified as primary or secondary. The velocity and position sensitivities of primate spindle afferents were determined. The mean dynamic index and mean dynamic sensitivity of secondary afferents were about 45% of the corresponding values for primary afferents. On the other hand, the position sensitivities of primary and secondary spindle afferents in the baboon were not significantly different.

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PubMed1976

Effects of fusimotor stimulation on dynamic and position sensitivities of spindle afferents in the primate.

The effects of stimulation of single static and dynamic fusimotor fibers on the dynamic sensitivity and position sensitivity of primary and secondary spindle afferents have been studied in the soleus muscle of the baboon. Static fusimotor fibers decreased the mean dynamic sensitivity of primary afferents at all rates of stretch and stimulation. The magnitude of the decrease in dynamic sensitivity increased as the rate of fusimotor stimulation was increased. Qualitatively similar effects were observed in secondary afferents. Static fusimotor stimulation had a strong excitatory effect on spindle afferent resting discharge and greatly increased the mean position sensitivity of both primary and secondary afferents. Dynamic fusimotor fibers increased the mean dynamic index of primary afferents at all rates of stretch and stimulation. The effect of dynamic fusimotor fibers on the mean dynamic sensitivity, however, was dependent on the rate of muscle stretch; at rates below 15 mm/s the dynamic sensitivity was substantially increased, whereas at rates greater than 15 mm/s it was either unchanged or decreased. Dynamic fusimotor fibers slightly decreased the mean position sensitivity of primary afferents.

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PubMed1976

Classification of fusimotor fibers in the primate.

The classification and distinguishing characteristics of fusimotor fibres of the baboon soleus muscle have been studied by determining the effects of single fusimotor fiber stimulation on the response of isolated spindle afferents to muscle stretch. As in the cat, fusimotor fibres in the baboon were divisible into static and dynamic types on the basis of the effect of their stimulation at 200/s on the dynamic index of the primary afferent. Single fusimotor fibres had the same qualitative effect-static or dynamic-on all the primary afferents they were found to influence. All static fusimotor fibres produced at least 1 to 1 driving of primary afferent discharge at 50/s if the muscle length was adjusted to optimize conditions for driving. In contrast, 31 of 32 dynamic fusimotor fibres did not produce driving of primary afferent discharge even though all were studied at many different muscle lengths and frequencies of stimulation. Therefore, fusimotor fibres in the baboon could be classified as static or dynamic on the basis of their ability to produce driving of the primary afferent. The ratio of isolated static to dynamic fusimotor fibers was 1.5 to 1. The mean conduction velocity of static fusimotor fibers was 24.1 m/s and that of dynamics was 20.2 m/s. Although the difference between these two means was statistically significant (P less than 0.001), the conduction velocity histograms of static and dynamic fusimotors overlapped, precluding classification by this means. Secondary afferents with one possible exception were concluded to be exclusively activated by static fusimotor fibers. Poststimulus effects of fusimotor stimulation on primary afferent response to stretch were studied. With intervals between the end of stimulation and the beginning of stretch of 0.1 s, dynamic fusimotor stimulation produced facilitation of the primary afferent response to stretch, whereas static fusimotor fibers produced depression.

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PubMed1976

Responses of cortical neurons (areas 3a and 4) to ramp stretch of hindlimb muscles in the baboon.

1. A study was made of the response of single cortical units in areas 3a and 4 to electrical stimulation of hindlimb muscle nerves and to ramp stretch of hindlimb muscles in baboons anesthetized with chloralose.2. Stimulation of hindlimb muscle nerves revealed a group I projection primarily to area 3a but with some input into adjacent area. 4. A major group II projection was found in area 4 adjacent to area 3a. A small number of area 3a neurons receive convergence from both group I and group II muscle afferents.3a. On the basis of their response pattern to ramp stretch, units were classified into one of six categories and their cytoarchitectonic location was determined. Units in area 3a had hynamic sensitivities equivalent to that of the primary spindle afferents. Although the discharge of some area 3a neurons also reflected differences in muscle length, most area 3a neurons had low position sensitivities. One unit type in area 3a did not respond to maintained muscle stretch and signaled only velocity of stretch.4. Units in area 4 had position sensitivities equivalent to that of primary and secondary spindle afferents. Although the discharge of some area 4 units reflected different velocities of muscle stretch, these units had dynamic sensitivities similar to those of secondary spindle afferents rather than those of primary afferents. One type of unit in area 4 had no dynamic component to muscle stretch and signaled only muscle length.5. The results demonstrate that there is a transfer of dynamic and position sensitivity from spindle afferents to cortical neurons. Furthermore, data processing has occurred because some units respond only to the steady-state length of muscle, while other units encode only the dynamic phase of stretch. This behavior is different from the responses to ramp stretch of either group I or group II muscle afferents in the baboon.6. The results demonstrate that single units in cerebral cortex can encode the information transmitted to the central nervous system by muscle spindle afferents. The purpose for which this information is used remains undetermined.

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