Showing papers on "Topographic map (neuroanatomy) published in 2014"

Patterns of cortical input to the primary motor area in the marmoset monkey.

Abstract: In primates the primary motor cortex (M1) forms a topographic map of the body, whereby neurons in the medial part of this area control movements involving trunk and hindlimb muscles, those in the intermediate part control movements involving forelimb muscles, and those in the lateral part control movements of facial and other head muscles. This topography is accompanied by changes in cytoarchitectural characteristics, raising the question of whether the anatomical connections also vary between different parts of M1. To address this issue, we compared the patterns of cortical afferents revealed by retrograde tracer injections in different locations within M1 of marmoset monkeys. We found that the entire extent of this area is unified by projections from the dorsocaudal and medial subdivisions of premotor cortex (areas 6DC and 6M), from somatosensory areas 3a, 3b, 1/2, and S2, and from posterior parietal area PE. While cingulate areas projected to all subdivisions, they preferentially targeted the medial part of M1. Conversely, the ventral premotor areas were preferentially connected with the lateral part of M1. Smaller but consistent inputs originated in frontal area 6DR, ventral posterior parietal cortex, the retroinsular cortex, and area TPt. Connections with intraparietal, prefrontal, and temporal areas were very sparse, and variable. Our results demonstrate that M1 is unified by a consistent pattern of major connections, but also shows regional variations in terms of minor inputs. These differences likely reflect requirements for control of voluntary movement involving different body parts.

An auditory colliculothalamocortical brain slice preparation in mouse.

Abstract: Key questions about the thalamus are still unanswered in part because of the inability to stimulate its inputs while monitoring cortical output. To address this, we employed flavoprotein autofluore...

Local cholinergic interneurons modulate GABAergic inhibition in the chicken optic tectum.

Abstract: The chicken optic tectum (TeO) and its mammalian counterpart, the superior colliculus, are important sensory integration centers. Multimodal information is represented in a topographic map, which plays a role in spatial attention and orientation movements. The TeO is organised in 15 layers with clear input and output regions, and further interconnected with the isthmic nuclei (NI), which modulate the response in a winner-takes-all fashion. While many studies have analysed tectal cell types and their modulation from the isthmic system physiologically, little is known about local network activity and its modulation in the tectum. We have recently shown with voltage-sensitive dye imaging that electrical stimulation of the retinorecipient layers results in a stereotypic response, which is under inhibitory control [S. Weigel & H. Luksch (2012) J. Neurophysiol., 107, 640–648]. Here, we analysed the contribution of acetylcholine (ACh) and the NI to evoked tectal responses using a pharmacological approach in a midbrain slice preparation. Application of the nicotinic ACh receptor (AChR) antagonist curarine increased the tectal response in amplitude, duration and lateral extent. This effect was similar but less pronounced when γ-aminobutyric acidA receptors were blocked, indicating interaction of inhibitory and cholinergic neurons. The muscarinic AChR antagonist atropine did not change the response pattern. Removal of the NI, which are thought to be the major source of cholinergic input to the TeO, reduced the response only slightly and did not result in a disinhibition. Based on the data presented here and the neuroanatomical literature of the avian TeO, we propose a model of the underlying local circuitry.

Studying motor cortex function using the rodent vibrissal system

Abstract: The function of the mammalian motor cortex was one of the first problems studied in neuroscience. But until today, the major principles of the workings of the motor cortex have remained conjectural. It is clear that motor cortex holds a topographic map of body parts. But does that mean that the motor cortex itself is undertaking the challenging task of converting motor plans (i.e., intended trajectories and effects of actions) into low level motor commands appropriate to drive the muscles? Work of many decades on motor function has revealed the existence of dedicated networks, the so-called central pattern generators (CPGs). Many, if not all of these CPGs, are located subcortically and are likely to be involved in the translation of motor plans into actual muscle contractions. Unfortunately the detailed circuitry and cellular elements of CPGs are only vaguely known. More recent work has elucidated continuous as well as discontinuous (discrete) mapping of the motor cortex to movement. For the quest of understanding motor cortex–CPG interactions, discontinuities are important because they allow us to dissect how neighboring motor cortex sites connect to different CPGs for different purposes—but driving the very same muscles. The rodent whisker motor system is a decidedly modular system. Neighboring cortical areas drive very distinct whisker movements used by the animals in different contexts. We argue that the modularity of the whisker system together with its great accessibility is promising to establish a model system for the interactions of the motor cortex and CPGs on the cellular and network levels and, thus, will also be of high value in understanding the more complex and continuously organized motor cortex of the arm/hand/finger system in primates.

Olfactory Map Formation in the Mouse

Abstract: In the mouse olfactory system, each olfactory sensory neuron (OSN) expresses only one functional odorant receptor (OR) species Furthermore, OSN axons bearing the same OR converge to a specific projection site in the olfactory bulb (OB), forming a glomerular structure Based on these two basic principles, odor information detected in the olfactory epithelium is converted to a topographic map of activated glomeruli in the OB During embryonic development, the olfactory map is formed by the combination of two genetically programmed processes One is OR-dependent projection along the anterior-posterior axis, and the other is OR-independent projection along the dorsal-ventral axis The map is further refined in an activity-dependent manner during the neonatal period Here, we discuss a recent progress of neural map formation in the mouse olfactory system

Simultaneous 3-dimensional Multi-point Recording System from Auditory Cortex and Thalamus in Rat

Abstract: 聴覚の情報処理では,音情報は蝸牛で神経信号に変 換 さ れ た 後 , 間 脳 の 視 床 の 内 側 膝 状 体 (Medial Geniculate Body; MGB)を経て,大脳皮質の聴皮質に伝 わる.神経信号の伝達経路は,末梢から中枢へのボト ムアップ方向でなく,中枢から末梢へのトップダウン 方向にも存在する.特に視床と聴皮質は互いに両方向 の解剖学的な結合を有しており,その相互作用は聴知 覚に多大な影響を及ぼしていると考えられる.しかし, 両者を多点同時計測して,視床・聴皮質システムの情 報処理機構を調べた試みはほとんどない. 視床と聴皮質は,それぞれ,明確な周波数マップを 有し,それらを情報処理の基盤にしていると考えられ ている.さらに,聴皮質は,解剖学的な特徴から,表 層からの深さに応じて,皮質内の情報処理層,視床か らの入力層,皮質からの出力層に分類できる [1]. 本研究では,これらの特徴に留意し,ラットの視床・ 聴皮質システムの 3 次元多点同時計測系を開発する.