Functional Properties of Neurons of the Anterior Ectosylvian Gyrus of the Cat

SUMMARY1. Cats anaesthetized with chloralose and paralysed with Flaxedil were used. The projections of muscle, joint and skin afferents to the cortical fold hidden in the anterior suprasylvian sulcus were investigated with micro-electrode recording techniques.2. Electrical stimulation of Group I muscle afferents from the contralateral forelimb evoked a negative focal potential (latency 5 msec) in a locus of 1-2 mm diameter found in the lower bank of the fold. In one experiment a response to Group I muscle afferents from the contralateral hind limb was observed. The Group I potentials disappeared after sectioning of the dorsal columns at C3.3. Groups II and III muscle afferents, low threshold skin afferents and joint afferents also evoked potentials in the Group I locus. It was concluded that the joint afferents originated mainly in the Ruffini endings of the joint capsule.4. Groups II and III muscle afferents, low threshold skin and low threshold joint afferents projected to the upper bank of the suprasylvian fold. A certain somatotopic arrangement was observed.5. The possibility of connexions between the cortex of the anterior suprasylvianfold andthe primary somato-sensory projection areas was discussed, as well as the organization ofthe loci in the fold in terms of cell colonies with different properties.

Section: Discussionmentioning

confidence: 87%

Somato‐sensory paths to the second cortical projection area of the group I muscle afferents

Landgren¹,

Silfvenius²,

Wolsk³

1967

“…The majority of the neurones responded with a latency shorter than 1 msec to a stimulus applied in the region of the post-cruciate dimple of S I. In addition, some of the neurones were discharged with a similar latency from another cortical focus which included area B of S II as described by Carreras & Andersson (1963) and a part of the anterior suprasylvian or coronal gyri on the other side of the anterior suprasylvian sulcus between the S I forelimb area and S II. The threshold intensity of the cortical stimulus required to evoke a short latency response in the thalamic neurones was lower in these two foci than in other cortical regions located in between or around them.…”

Section: Methodsmentioning

confidence: 85%

The thalamic relay and cortical projection of Group I muscle afferents from the forelimb of the cat

Andersson¹,

Landgren²,

Wolsk³

1966

Self Cite

112

SUMMARY1. Stimulation of Group I muscle afferents in contralateral forelimb nerves evoked a response in nucleus ventralis posterolateralis (VPL) in the thalamus of the cat. This response was located in the rostral twothirds of VPL in a narrow zone near the dorsomedial border of the nucleus.2. Group I afferents in nerves from more than one of the muscles in the contralateral forelimb often excited the same thalamic relay cell. In addition these cells were often discharged by skin afferents from the contralateral forelimb. They were not affected by electrical stimulation of the dorsal column-lemniscal or the spino-cervico-lemniscal paths from the contralateral hind limb.3. In experiments with peripheral conduction paths of similar length, the latency of the thalamic focal potential evoked by stimulation of Group I muscle afferents in the nerve to m. extensor carpi radialis was 3x8 S.E. + 0-1 msec, and that of the focal potential evoked by skin afferents (n. radialis superficialis) in the centromedial part ofVPL was 4x3 + 0.1 msec. 4. The majority of the thalamic neurones discharged by Group I muscle afferents responded with a latency shorter than 1 msec to electrical stimulation of the cerebral cortex in the region of the post-cruciate dimple. A considerable number of the thalamic Group I relay cells were also discharged with a similar short latency from another cortical focus located on either side of the anterior suprasylvian sulcus near the S II hind limb areas. These responses were considered to be antidromic in nature, and the findings were interpreted as indicating two separate cortical projection areas for the Group I path. The second projection area was assumed to be located in the cortical fold formed by the anterior suprasylvian sulcus.5. Cortical stimulation also excited the thalamic Group I relay cells trans-synaptically. Trans-synaptic excitation with short (1-2 msec) and * Present address: University of Michigan, Ann Arbor, U.S.A. CENTRAL PROJECTIONS OF MUSCLE AFFERENTS 577 longer (2-7 msec) latency was observed. The cortical focus near the S II area was particularly potent in evoking trans-synaptic excitation in the thalamic region where the Group I relays were located.

“…These authors showed that the anterior ectosylvian gyrus received primary auditory projections, because the latency of the evoked potential was just as short as that of the response evoked in the primary auditory projection area, and because the auditory response remained unaltered after removal of this area. Convergence between somato-sensory and auditory paths on VESTIBULAR PROJECTIONS TO CORTEX to single cortical units were described by Andersson (1962) and by Carreras & Andersson (1963). Such units were particularly common in the posterior part of the anterior ectosylvian gyrus, a region which was referred to as S II A by Carreras & Andersson (1963).…”

Section: Discussionmentioning

confidence: 95%

“…Convergence between somato-sensory and auditory paths on VESTIBULAR PROJECTIONS TO CORTEX to single cortical units were described by Andersson (1962) and by Carreras & Andersson (1963). Such units were particularly common in the posterior part of the anterior ectosylvian gyrus, a region which was referred to as S II A by Carreras & Andersson (1963). The part of the suprasylvian fold, where the cochlear responses were located, is continuous with S II A (cf.…”

Section: Discussionmentioning

confidence: 97%

“…Diagram of the cortex sihowing the projection areas of the vestibular (vertical hatching) and cochlear (horizontal hatching) nerves in the suprasylvian fold in relation to the projection areas of the Group I muscle afferents from the contralateral forelimnb in the fold (stippled area). and in Pcd, the contralateral maxillary trigeminal fields with initially positive cortical surface potentials (T), the projection area of the contralateral superficial radial (SIlf) and sural (SIIh) nerves and area S II A of Carreras & Andersson (1963). Ss: opened and flattened out suprasylvian fold; a: upper bank; b: lower bank.…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Vestibular, cochlear and trigeminal projections to the cortex in the anterior suprasylvian sulcus of the cat

Landgren¹,

Silfvenius²,

Wolsk³

1967

SUMMARY1. Cats anaesthetized with chloralose were used. Potentials evoked by electrical stimulation of the vestibular, cochlear, facial, trigeminal and chorda tympani nerves were recorded with micro-electrodes in the cortex in the anterior syprasylvian sulcus.2. Negative focal potentials with a latency of 3 msec were evoked by stimulation of the contralateral and ipsilateral vestibular nerves. These potentials were located in the lower and upper banks of the sulcus at a level just caudal to the projection of the Group I muscle afferents to the lower bank.3. The cochlear projections were located mainly in the lower bank partially overlapping the vestibular and the Group I fields.4. Trigeminal responses were recorded in both banks of the sulcus but were of largest amplitude and shortest latency rostrally in the upper bank. The potentials evoked by the chorda tympani had a similar distribution but were of low amplitude.5. The hypothesis is suggested, that the cortex in the anterior suprasylvian sulcus plays a role in the orientation of the body and head towards auditory stimuli.