Search PubMed⌕ Search
Home/Archive/PubMed

PubMed · 11160519

Synchronization in monkey motor cortex during a precision grip task. I. Task-dependent modulation in single-unit synchrony.

S N Baker·R Spinks·A Jackson·R N Lemon
View original source ↗Export metadata ↓

Abstract

Neural synchronization in the cortex, and its potential role in information coding, has attracted much recent attention. In this study, we have recorded long spike trains (mean, 33,000 spikes) simultaneously from multiple single neurons in the primary motor cortex (M1) of two conscious macaque monkeys performing a precision grip task. The task required the monkey to use its index finger and thumb to move two spring-loaded levers into a target, hold them there for 1 s, and release for a food reward. Synchrony was analyzed using a time-resolved cross-correlation method, normalized using an estimate of the instantaneous firing rate of the cell. This was shown to be more reliable than methods using trial-averaged firing rate. A total of 375 neurons was recorded from the M1 hand area; 235 were identified as pyramidal tract neurons. Synchrony was weak [mean k' = 1.05 +/- 0.04 (SD)] but widespread among pairs of M1 neurons (218/1359 pairs with above-chance synchrony), including output neurons. Synchrony usually took the form of a broad central peak [average width, 18.7 +/- 8.7 (SD) ms]. There were marked changes during different phases of the task. As a population, synchrony was greatest during the steady hold period in striking contrast to the averaged cell firing rate, which was maximal when the animal was moving the levers into target. However, the modulation of synchrony during task performance showed considerable variation across individual cell pairs. Two types of synchrony were identified: oscillatory (with periodic side lobes in the cross-correlation) and nonoscillatory. Their relative contributions were quantified by filtering the cross-correlations to exclude either frequencies from 18 to 37 Hz or all higher and lower frequencies. At the peak of population synchrony during the hold period, about half (51.7% in one monkey, 56.2% in the other) of the synchronization was within this oscillatory bandwidth. This study provides strong support for assemblies of neurons being synchronized during specific phases of a complex task with potentially important consequences for both information processing within M1 and for the impact of M1 commands on target motoneurons.

Explore related subjects

Action PotentialsAnimalsFemaleHand StrengthMacaca mulattaMotor CortexNeuronsOscillometryReaction TimeJournal ArticleResearch Support, Non-U.S. Gov't

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

S N Baker, R Spinks, A Jackson, R N Lemon. 2001. Synchronization in monkey motor cortex during a precision grip task. I. Task-dependent modulation in single-unit synchrony.. https://doi.org/10.1152/jn.2001.85.2.869

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

PubMed2007

Relationship of complex spike synchrony bands and climbing fiber projection determined by reference to aldolase C compartments in crus IIa of the rat cerebellar cortex.

Synchronous complex spike (CS) activity occurs most often among cerebellar Purkinje cells located in a narrow longitudinal (parasagittal) strip of cortex (synchrony band). The relationship of the anatomical organization of the olivocerebellar projection to these synchrony bands has not been investigated in detail. Thus, we studied this relationship by using the aldolase C (zebrin II) expression pattern, another landmark for the cerebellar longitudinal organization, as a reference frame in rat crus IIa. Crus IIa consists of 10 aldolase C-positive and -negative longitudinal compartments. Aldolase C labeling after multiple-electrode recording of CSs indicated that in lateral crus IIa (compartments 5+ to 7+) synchrony bands were generally constrained to single compartments. In contrast, in medial crus IIa (compartments 4a- to 5a-) the synchrony within and across the compartments was much higher than in lateral crus IIa, resulting in wide synchrony bands covering multiple compartments. Retrograde labeling of olivary neurons by injections of biotinylated dextran amine into aldolase C compartments in crus IIa showed that compartments in medial crus IIa were all innervated by the caudal part of the medial accessory olive. On the other hand, each aldolase C compartment in the lateral crus IIa was innervated by a region in a different subnucleus in the rostral inferior olive. These regions in different subnuclei were located close to each other. These results suggest that CS synchrony bands reflect the olivocerebellar compartmental projection pattern and neuronal coupling within a particular olivary subnucleus, and that medial and lateral crus IIa may be functionally distinct.

Action Potentials↗
PubMed2007

Motoneurons of the flight power muscles of the blowfly Calliphora erythrocephala: structures and mutual dye coupling.

The morphologies of the motoneurons of the dorsolongitudinal and the three dorsoventral flight power muscles (DLM, DVM 1-3) of Calliphora were investigated by means of cobalt backfills and intracellular biocytin stainings. The DLM is innervated by four prothoracic motoneurons supplying the four ventral muscle fibers and one mesothoracic motoneuron supplying the two dorsal fibers. The three fibers of the DVM 1 and the two fibers of the DVM 2 are innervated by five mesothoracic motoneurons, whereas the two fibers of the DVM 3 are innervated by two prothoracic motoneurons. In general, the motoneurons of each muscle have a common ventral soma cluster located in a characteristic position on the ipsilateral side of the thoracic ganglion, show similar dendritic arborizations in the mesothoracic wing neuropil, and have the same axon pathway. Only the soma of the common motoneuron of two dorsal fibers of the DLM is situated dorsally in the contralateral hemiganglion. The motoneurons of each muscle were found to be strongly dye coupled with each other, indicating that they are connected by gap junctions. In addition, the motoneurons of each muscle establish characteristic coupling patterns with the motoneurons of the other flight power muscles on both sides of the thorax and with two bilateral groups of local mesothoracic interneurons. The revealed coupling patterns are assumed to be of major relevance for the generation the characteristic, rhythmic flight activity of the motoneurons described in previous studies.

Action Potentials↗
PubMed2007

Systemic signalling in barley through action potentials.

Using apoplastic voltage- and ion selective microprobes, in barley leaves action potentials (APs) have been measured, which propagate acropetally as well as basipetally from leaf to leaf or from root to leaf following the application of mild salt stress (e.g. 30-50 mM KCl or NH(4)Cl) or amino acids (e.g. 1 mM glutamic acid or 5 mM GABA). Voltage changes were biphasic, followed an 'all-or-none' characteristic, and propagated at 20-30 cm min(-1) irrespective of the direction. With the salt-induced APs, a strong initial depolarization is the main AP-releasing factor that first causes Ca(2+) influx and then anion efflux. Ca(2+) influx coincides with an initial slower depolarization, the rapid anion efflux causes the typical voltage 'break-through'. Subsequently, K(+)-efflux starts after the depolarizing voltage has passed the K(+) equilibrium potential (inversion of the K(+) driving force). Glutamic acid and GABA induce APs not through membrane depolarization, but presumably by binding to a putative receptor or to ligand-gated Ca(2+)-conducting channels, respectively, followed by Ca(2+) induced activation of anion efflux. APs are accompanied by transient apoplastic pH increase (about 1 unit), and by cytoplasmic pH decrease (about 0.5 units). The apoplastic pH change is interpreted as an indicator of stress, the cytoplasmic pH change as a prerequisite for defence related gene activation. Since APs are released by agents added in a moderate concentration range, it is suggested that they may serve as first and fast systemic signals following attack from pathogens.

Action Potentials↗