Reduction Of Sensory Input Research Articles

Perturbed neural activity disrupts cerebral angiogenesis during a postnatal critical period

During the neonatal period, activity-dependent neural circuit remodeling coincides with growth and refinement of the cerebral microvasculature1,2. Whether neural activity also influences the patterning of the vascular bed is not known. Here we show in neonatal mice, that neither reduction of sensory input through whisker trimming nor moderately increased activity by environmental enrichment affected cortical microvascular development. Surprisingly however, chronic stimulation by repetitive sounds, whisker deflection, or motor activity led to a near arrest of angiogenesis in barrel, auditory, and motor cortices, respectively. Chemically-induced seizures also caused robust reductions in microvascular density. Altering neural activity in adult mice, however, did not affect the vasculature. Histological analysis and time-lapse in vivo two-photon microscopy revealed that hyperactivity did not lead to cell death or pruning of existing vessels but rather reduced endothelial proliferation and vessel sprouting. This anti-angiogenic effect was prevented by administration of the nitric oxide synthase (NOS) inhibitor L-NAME and in mice with neuronal and inducible NOS deficiency, suggesting that excessive nitric oxide released from hyperactive interneurons and glia inhibited vessel growth. Vascular deficits persisted long after cessation of hyperstimulation, providing evidence for a critical period after which proper microvascular patterning cannot be re-established. Reduced microvascular density diminished the ability of the brain to compensate for hypoxic challenges, leading to dendritic spine loss in regions distant from capillaries. Therefore, excessive sensorimotor stimulation and repetitive neural activation during early childhood may cause lifelong deficits in microvascular reserve, which could have important consequences on brain development, function, and pathology.

Sensory experience selectively regulates transmitter synthesis enzymes in interglomerular circuits

Sensory experience influences brain organization and function. A particularly striking example is in the olfactory bulb where reduction of odorant sensory signals profoundly down-regulates dopamine in glomerular neurons. There are two large populations of glomerular inhibitory interneurons: (1) GABAergic periglomerular (PG) cells, whose processes are limited to a single glomerulus, regulate intraglomerular processing and (2) DAergic-GABAergic short axon (SA) cells, whose processes contact multiple glomeruli, regulate interglomerular processing. The inhibitory neurotransmitter GABA is synthesized from L-glutamic acid by the enzyme glutamic acid decarboxylase (GAD) of which there are two major isoforms: GAD65 and GAD67. GAD65 is expressed in uniglomerular PG cells. GAD67 is expressed by SA cells, which also co-express the rate-limiting enzyme for dopamine synthesis, tyrosine hydroxylase (TH). Deafferentation or sensory deprivation decreases TH expression but it is not known if sensory input alters GAD isoforms. Here we report that either deafferentation or reduction of sensory input by nares occlusion significantly reduced GAD67 protein and the number of SA cells expressing GAD67. However, neither manipulation altered GAD65 protein or the number of GAD65 PG cells. These findings show that sensory experience strongly impacts transmitter regulation in the circuit that controls neural processing across glomeruli but not in the circuit that regulates intraglomerular processing.

Contralateral hand anesthesia transiently improves poststroke sensory deficits

To test a possible strategy to alleviate somatosensory deficits after stroke. Here, we applied ischemic nerve block to the intact hand of patients with chronic stroke, which in healthy subjects elicits improvements in sensibility of the other hand. We found that sensibility in the affected hand improved with intact hand anesthesia, but not with intact foot anesthesia or no anesthesia. We conclude that reduction of sensory input from the intact hand leads to site-specific improvements in tactile discriminative skills in the affected hand after the period of anesthesia, a potentially relevant finding in designing neurorehabilitative interventions.

Physostigmine for the Acute Treatment of Restless Legs Syndrome

We present a case report of an acute episode of restless legs syndrome that interfered with the performance of a diagnostic imaging procedure of the cervical spine. The patient had a 19-yr history of restless leg syndrome with periodic limb movements during sleep. Treatment with additional sedation and opioids did not alleviate the leg movements. IV administration of 1 mg of physostigmine eradicated all extraneous leg motion.

Wahnsyndrome bei sensorischer Beeinträchtigung - Überblick und Modellvorstellungen

Since Kraepelin's description of the "paranoia of the deaf" in 1915, the connection between sensory impairment and paranoid states in old age has been repeatedly confirmed. Parallels may be drawn to delusional syndromes caused or triggered by linguistic isolation, sensory aphasia and the perceptual disturbances in early schizophrenia. An overview on the different delusional phenomena in sensory-perceptual dysfunction is given, followed by a pathogenetic model proposed in analogy to the "perceptual-release" theory of hallucinations: Reduction of sensory input and blurring of afferent schemas in the perception process result in a compensatory stimulation and "release" of paranoid patterns of information processing. Consistency of perception is reestablished at the price of rigid, delusional interpretation of ambiguous social situations.

Central Nervous System Changes Related to the Reduction of Visual Input in a Naturally Blind Fish (Astyanax hubbsi)

Tectal anatomy and physiology of the blind cave characin, Astyanax hubbsi , have been compared with that of its sighted ancestor Astyanax mexicanus (the river fish) and with goldfish. Normal and experimental neuroanatomic methods have revealed that, with the exception of a greatly reduced retinotectal projection, connectivity and structure of cave fish tecta are similar to those described in sighted species. It appears that the rudimentary retinotectal input is nonfunctional, since no tectal evoked responses could be elicited with electrical or visual stimulation of the optic cyst, and all attempts to visually condition cave fish were unsuccessful. Attempts have also been made to record somatosensory, auditory and lateral line activity in the tecta of the blind and sighted fish. A sparse somatic representation was found in the deeper portion of the sighted fish tecta which contrasts with a dense, well-organized one in the cave fish. No tectal responses were found to auditory or lateral line stimuli. CNS plasticity is discussed in relation to studies of fish, amphibians, reptiles, birds and mammals, in which a reduction of sensory input by any one of a number of means has resulted in alterations of structure and function.

Visual-evoked response in lateral hypothalamic neglect

Visual-evoked responses were recorded bilaterally from the occipitoparietal region of six split-brain cats, before and 2 days after a unilateral hypothalamic lesion had produced a contralateral sensorimotor neglect syndrome. No consistent change in each visual-evoked response was detected, but there was an average increase in voltage in slow components on the side of the lesion compared to changes on the intact side. It is concluded that sensorimotor neglect is not associated with reduction of sensory input, and that the changed cortical synchrony accompanying this syndrome therefore reflects disruption of a nonsensory mechanism.

Observations of sensory deprivation in a life-threatening situation.

The illusions and hallucinations experienced by two miners trapped together for six days in a situation of marked reduction of sensory input are described. Their mental productions were chiefly related to wishes to be rescued, either by simple means such as doorways and stairs or by more powerful forces such as the Pope. Neither man exhibited evidence of psychosis or marked mental abnormality when examined two and three days after rescue.