Influence of Implantation Depth on the Performance of Intracortical Probe Recording Sites

Microelectrode arrays (MEAs) enable the recording of electrical activity from cortical neurons which has implications for basic neuroscience and neuroprosthetic applications. The design space for MEA technology is extremely wide where devices may vary with respect to the number of monolithic shanks as well as placement of microelectrode sites. In the present study, we examine the differences in recording ability between two different MEA configurations: single shank (SS) and multi-shank (MS), both of which consist of 16 recording sites implanted in the rat motor cortex. We observed a significant difference in the proportion of active microelectrode sites over the 8-week indwelling period, in which SS devices exhibited a consistent ability to record activity, in contrast to the MS arrays which showed a marked decrease in activity within 2 weeks post-implantation. Furthermore, this difference was revealed to be dependent on the depth at which the microelectrode sites were located and may be mediated by anatomical heterogeneity, as well as the distribution of inhibitory neurons within the cortical layers. Our results indicate that the implantation depth of microelectrodes within the cortex needs to be considered relative to the chronic performance characterization.

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Early pyrexia after endovascular aneurysm repair: are cultures needed?

Annals of The Royal College of Surgeons of England ◽

10.1308/003588411x12851639107719 ◽

2011 ◽

Vol 93 (2) ◽

pp. 111-113 ◽

Cited By ~ 8

Author(s):

L Corfield ◽

J Chan ◽

T Chance ◽

N Wilson

Keyword(s):

Endovascular Aneurysm Repair ◽

Blood Cultures ◽

Stent Insertion ◽

Out Of Hours ◽

Microbiological Investigation ◽

Significant Difference ◽

Aneurysm Repair ◽

Infective Complications ◽

Post Implantation

INTRODUCTION The post-implantation syndrome after endovascular aneurysm repair (EVAR) is increasingly recognised. However, when non-vascular trainees are responsible for the care of these patients out of hours, many are investigated if pyrexial. This study assesses the role of microbiological investigations in pyrexia after endovascular aneurysm repair. PATIENTS AND METHODS The notes of 75 EVAR patients were reviewed retrospectively. The incidence of postoperative pyrexia and infective complications were calculated and the result of any cultures obtained. RESULTS Overall, 58 (77.3%) patients were pyrexial with 48 h of stent insertion. Twenty-four had blood cultures and 12 had urine cultures taken within 48 h of surgery. All of these cultures were negative. However, of those with a pyrexia after 48 h, one of nine blood cultures and two of 11 urine cultures grew organisms. Five pyrexial patients and one apyrexial patient developed a wound infection (a non-significant difference, P = 1.00). CONCLUSIONS Pyrexia within 48 h of EVAR is common. Microbiological investigation in the first 48 h in these patients is unrewarding. After 48 h, cultures are more likely to show growth. Although each patient must be assessed clinically for signs of sepsis, blood and urine cultures within 48 h of EVAR are generally unnecessary.

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Two-dimensional receptive-field organization in striate cortical neurons of the cat

Visual Neuroscience ◽

10.1017/s0952523800003011 ◽

1994 ◽

Vol 11 (4) ◽

pp. 703-720 ◽

Cited By ~ 10

Author(s):

Ming Sun ◽

A. B. Bonds

Keyword(s):

Receptive Field ◽

Cortical Neurons ◽

Ocular Dominance ◽

Receptive Fields ◽

Field Size ◽

Two Dimensional ◽

Cortical Layers ◽

Field Organization ◽

Receptive Field Organization ◽

Cortical Receptive Fields

AbstractThe two-dimensional organization of receptive fields (RFs) of 44 cells in the cat visual cortex and four cells from the cat LGN was measured by stimulation with either dots or bars of light. The light bars were presented in different positions and orientations centered on the RFs. The RFs found were arbitrarily divided into four general types: Punctate, resembling DOG filters (11%); those resembling Gabor filters (9%); elongate (36%); and multipeaked-type (44%). Elongate RFs, usually found in simple cells, could show more than one excitatory band or bifurcation of excitatory regions. Although regions inhibitory to a given stimulus transition (e.g. ON) often coincided with regions excitatory to the opposite transition (e.g. OFF), this was by no means the rule. Measurements were highly repeatable and stable over periods of at least 1 h. A comparison between measurements made with dots and with bars showed reasonable matches in about 40% of the cases. In general, bar-based measurements revealed larger RFs with more structure, especially with respect to inhibitory regions. Inactivation of lower cortical layers (V-VI) by local GABA injection was found to reduce sharpness of detail and to increase both receptive-field size and noise in upper layer cells, suggesting vertically organized RF mechanisms. Across the population, some cells bore close resemblance to theoretically proposed filters, while others had a complexity that was clearly not generalizable, to the extent that they seemed more suited to detection of specific structures. We would speculate that the broadly varying forms of cat cortical receptive fields result from developmental processes akin to those that form ocular-dominance columns, but on a smaller scale.

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Fast-spiking GABA circuit dynamics in the auditory cortex predict recovery of sensory processing following peripheral nerve damage

eLife ◽

10.7554/elife.21452 ◽

2017 ◽

Vol 6 ◽

Cited By ~ 27

Author(s):

Jennifer Resnik ◽

Daniel B Polley

Keyword(s):

Peripheral Nerve ◽

Auditory Cortex ◽

Sensory Processing ◽

Cortical Neurons ◽

Sensory Nerve ◽

Intracortical Inhibition ◽

Nerve Fibers ◽

Nerve Damage ◽

Inhibitory Neurons ◽

Sound Processing

Cortical neurons remap their receptive fields and rescale sensitivity to spared peripheral inputs following sensory nerve damage. To address how these plasticity processes are coordinated over the course of functional recovery, we tracked receptive field reorganization, spontaneous activity, and response gain from individual principal neurons in the adult mouse auditory cortex over a 50-day period surrounding either moderate or massive auditory nerve damage. We related the day-by-day recovery of sound processing to dynamic changes in the strength of intracortical inhibition from parvalbumin-expressing (PV) inhibitory neurons. Whereas the status of brainstem-evoked potentials did not predict the recovery of sensory responses to surviving nerve fibers, homeostatic adjustments in PV-mediated inhibition during the first days following injury could predict the eventual recovery of cortical sound processing weeks later. These findings underscore the potential importance of self-regulated inhibitory dynamics for the restoration of sensory processing in excitatory neurons following peripheral nerve injuries.

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Development of a Culture-ripened Semi-hard Kishk-cheese Containing Bourghol or Semolina

Journal of Food Research ◽

10.5539/jfr.v8n1p21 ◽

2018 ◽

Vol 8 (1) ◽

pp. 21

Author(s):

Elham Hajj ◽

Rita Yaacoub ◽

Nadine Al-Arja ◽

Samir Scandar ◽

Hussein Dib

Keyword(s):

Physicochemical Parameters ◽

Sharp Increase ◽

Free Amino ◽

Marked Decrease ◽

Titratable Acidity ◽

Starter Cultures ◽

Oxidation Rates ◽

Significant Difference ◽

Depletion Rate ◽

Tbars Values

In order to develop a new Kishk-based ripened semi-hard cheese, two different wheat types, namely Bourghol and Semolina, were used. The process involved adding together cereal, goat strained yogurt, starter cultures and rennin enzyme. Physicochemical parameters and sensory attributes were assessed during 4 weeks of ripening at 10°C. The results showed an increase in titratable acidity, pH and solubility index in both types of cheese over ripening period reaching final levels of 1.95%, 3.75 and 85% respectively. Free amino acids were accumulating in Semolina cheese (17.75 mg Leu/g in final product), with a sharp increase after week 2 concurring with a marked decrease in residual lactose. A higher depletion rate of residual lactose was observed for Semolina cheese (49% in Semolina vs 40% in Bourghol) (p<0.05), reflecting better utilization of lactose by LAB. Both types of cheese showed limited oxidation rates (low peroxide and TBARS values) and balanced lipolysis, where FFA formed by the latter decreased after week 2. Texture analysis showed that Kishk-cheese made using Bourghol was always harder (p<0.05) than that of Semolina. Sensory analysis showed that cheese obtained from Bourghol tends to be more yellowish, harder with closed and crumbly body, together with a grainy texture in mouth and pronounced cereal flavor, whereas cheese obtained from Semolina tends to be sour, creamy with a sticky and cohesive texture, and rich lactic, buttery and cheesy flavors. Hedonic tests showed a significant difference (p<0.05) in preference between both types of cheese where Semolina was always preferred except for odor.

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Transient and prolonged effects of acetylcholine on responsiveness of cat somatosensory cortical neurons

Journal of Neurophysiology ◽

10.1152/jn.1988.59.4.1253 ◽

1988 ◽

Vol 59 (4) ◽

pp. 1253-1276 ◽

Cited By ~ 98

Author(s):

R. Metherate ◽

N. Tremblay ◽

R. W. Dykes

Keyword(s):

Receptive Field ◽

Somatosensory Cortex ◽

Cortical Neurons ◽

Receptive Fields ◽

Fixed Dose ◽

Cortical Layers ◽

Afferent Inputs ◽

Time Periods ◽

Layer I ◽

Layer Vi

1. Two-hundred and seven neurons were examined for changes in their responsiveness during the iontophoretic administration of acetylcholine (ACh) in barbiturate-anesthetized cats. 2. The laminar locations of 78 cells were determined. Cholinoceptive neurons were found in all cortical layers and ranged from 50% of the cells tested in layer I to 78% in layer VI. 3. When the responsiveness of a neuron was measured by the magnitude of the discharge generated by a fixed dose of glutamate, 30 of 47 cases (64%) were potentiated, and 4 (8%) were depressed when ACh was administered during glutamate-induced excitation. 4. ACh administered during glutamate excitation was significantly more effective in altering neuronal responsiveness than was ACh administered alone (P less than 0.001). 5. When the responsiveness of a neuron was measured by the magnitude of the discharge generated by a standard somatic stimulus applied to the receptive field, 42 of 52 cases (81%) were potentiated during ACh application. This was again different from ACh treatment alone where only 4 of 27 tests (15%) resulted in subsequent enhancement of the response to somatic stimuli. 6. ACh generally increased the responsiveness of neurons with peripheral receptive fields and caused the appearance of a receptive field in some cells lacking one. 7. In many cases the changes in excitability, as measured by responses either to glutamate or to somatic stimulation, remained for prolonged time periods. When glutamate was used to test excitability, 34% (16 of 47) of the enhancements lasted more than 5 min. When somatic stimuli were used 29% (15 of 52) lasted more than 5 min. With both measures some neurons still displayed enhanced responses more than 1 h after the treatment with ACh. 8. ACh appears to act as a permissive agent that allows modification of the effectiveness with which previously existing afferent inputs drive somatosensory cortical neurons. 9. This mechanism to alter neuronal responsiveness has many of the characteristics necessary to account for the reorganization observed in somatosensory cortex following alterations in its afferent drive and may be related to some forms of learning and memory.

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Modulation of nociception by corticotrigeminal pathway- A narrative review

Mediscope ◽

10.3329/mediscope.v7i1.47140 ◽

2020 ◽

Vol 7 (1) ◽

pp. 51-57

Author(s):

Sayema Ainan

Keyword(s):

Nervous System ◽

Trigeminal Nerve ◽

Cortical Neurons ◽

Pain Perception ◽

Pain Treatment ◽

Early Stage ◽

Short Review ◽

Inhibitory Neurons ◽

Pain Sensation

Management of chronic pain is one of the most important reason to which medications are given. Traditional medicines which have been used to relieve pain are having a number of limitations. Therefore, novel therapies for pain treatment are essential. Our nervous system can process any kind of injurious stimuli, which is known as nociception. The mechanism of nociception involves a complex interaction of peripheral and central nervous system structures. Brain or cerebral cortex has its own controlling mechanism for pain perception. Trigeminal nerve is the fifth cranial nerve and it receives pain sensation from oro- and craniofacial region and sends the information up to cortex. Recent investigations demonstrate another important role of cortical neurons in addition to pain perception, that is, corticotrigeminal (cortex to trigeminal) pathway excites neurons in the trigeminal nerve that leads to decrease in the pain response induced by noxious stimuli. Thus, as this mechanism can be induced at early stage of nociception, it may reduce the pain sensation. So, the corticotrigeminal pathway could be a new potential target for pain therapies. This short review revisits the concepts how stimulation of primary somatosensory cortex can be transmitted via corticotrigeminal tract which aim for the inhibitory neurons in spinal trigeminal nucleus caudalis (SpVc) and thus potentially generate a feedforward inhibition, explaining the pain modulatory role of the corticotrigeminal pathway. Mediscope Vol. 7, No. 1: Jan 2020, Page 51-57

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Timing of neuronal death in trkA, trkB and trkC mutant embryos reveals developmental changes in sensory neuron dependence on Trk signalling

Development ◽

10.1242/dev.122.10.3255 ◽

1996 ◽

Vol 122 (10) ◽

pp. 3255-3261 ◽

Cited By ~ 5

Author(s):

L.G. Pinon ◽

L. Minichiello ◽

R. Klein ◽

A.M. Davies

Keyword(s):

Neuronal Death ◽

Tyrosine Kinases ◽

Marked Decrease ◽

Trigeminal Ganglia ◽

Wild Type ◽

Embryonic Mouse ◽

Target Field ◽

Significant Difference

The sensory neurons of the embryonic mouse trigeminal ganglion are supported in culture by different neurotrophins at successive stages of development. Initially the neurons survive in response to BDNF and NT3 and later switch to becoming NGF-dependent (Buchman, V. I. and Davies, A. M. (1993), Development 118, 989–1001). To determine if this in vitro switch in neurotrophin responsiveness is physiologically relevant, we studied the timing of neuronal death in the trigeminal ganglia of embryos that are homozygous for null mutations in the trkA, trkB and trkC genes, which encode receptor tyrosine kinases for NGF, BDNF and NT3, respectively. In wild-type embryos, the number of pyknotic nuclei increased from E11 to peak between E13 and E14, and decreased gradually at later ages, becoming negligible by birth. Neuronal death in the trigeminal ganglia of trkA−/− embryos also peaked between E13 and E14, but was almost threefold greater than in wild-type embryos at this stage. Whereas there was no significant difference between the number of pyknotic nuclei in trkA−/− and wild-type embryos at E11 and E12, there was a substantial increase in the number of pyknotic nuclei in the trigeminal ganglia of trkB−/− at these earlier stages. Counts of the total number of neurons in E13 trigeminal ganglia revealed a marked decrease in trkB−/− but not trkA−/− or trkC−/− embryos. Consistent with the later onset of excessive neuronal death in trkA−/− embryos, there was a marked decrease in the neuronal complement of the trigeminal ganglia of trkA−/− embryos at E15. These results demonstrate that TrkB signalling is required for the in vivo survival of many trigeminal neurons during the early stages of target field innervation before they become NGF-dependent.

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Modulation of auditory responses by visual inputs in the mouse auditory cortex

10.1101/2021.01.22.427870 ◽

2021 ◽

Author(s):

Sudha Sharma ◽

Hemant Kumar Srivastava ◽

Sharba Bandyopadhyay

Keyword(s):

Auditory Cortex ◽

Auditory Processing ◽

Cortical Neurons ◽

Visual Information ◽

Visual Stimulation ◽

Inhibitory Neurons ◽

Visual Responses ◽

Full Field ◽

Auditory Responses ◽

Layer 2

AbstractSo far, our understanding on the role of the auditory cortex (ACX) in processing visual information has been limited to infragranular layers of the ACX, which have been shown to respond to visual stimulation. Here, we investigate the neurons in supragranular layers of the mouse ACX using 2-photon calcium imaging. Contrary to previous reports, here we show that more than 20% of responding neurons in layer2/3 of the ACX respond to full-field visual stimulation. These responses occur by both excitation and hyperpolarization. The primary ACX (A1) has a greater proportion of visual responses by hyperpolarization compared to excitation likely driven by inhibitory neurons of the infragranular layers of the ACX rather than local layer 2/3 inhibitory neurons. Further, we found that more than 60% of neurons in the layer 2/3 of A1 are multisensory in nature. We also show the presence of multisensory neurons in close proximity to exclusive auditory neurons and that there is a reduction in the noise correlations of the recorded neurons during multisensory presentation. This is evidence in favour of deep and intricate visual influence over auditory processing. The results have strong implications for decoding visual influences over the early auditory cortical regions.Significance statementTo understand, what features of our visual world are processed in the auditory cortex (ACX), understanding response properties of auditory cortical neurons to visual stimuli is important. Here, we show the presence of visual and multisensory responses in the supragranular layers of the ACX. Hyperpolarization to visual stimulation is more commonly observed in the primary ACX. Multisensory stimulation results in suppression of responses compared to unisensory stimulation and an overall decrease in noise correlation in the primary ACX. The close-knit architecture of these neurons with auditory specific neurons suggests the influence of non-auditory stimuli on the auditory processing.

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Evolution of Neocortex for Sensory Processing

Oxford Research Encyclopedia of Neuroscience ◽

10.1093/acrefore/9780190264086.013.111 ◽

2019 ◽

Author(s):

Jon H. Kaas

Keyword(s):

Sensory Processing ◽

Cortical Neurons ◽

Pyramidal Neurons ◽

Motor Behavior ◽

Single Layer ◽

Small Region ◽

Inhibitory Neurons ◽

Dorsal Cortex ◽

Structural Differentiation ◽

Cortical Areas

The neocortex is a part of the forebrain of mammals that is an innovation of mammal-like “reptilian” synapsid ancestors of early mammals. This neocortex emerged from a small region of dorsal cortex that was present in earlier ancestors and is still found in the forebrain of present-day reptiles. Instead of the thick structure of six layers of cells (five layers) and fibers (one layer) of neocortex of mammals, the dorsal cortex was characterized by a single layer of pyramidal neurons and a scattering of small, largely inhibitory neurons. In reptiles, the dorsal cortex is dominated by visual inputs, with outputs that relate to behavior and memory. The thicker neocortex of six layers in early mammals was already divided into a number of functionally specialized zones called cortical areas that were predominantly sensory in function, while relating to important aspects of motor behavior via subcortical projections. These early sensorimotor areas became modified in various ways as different branches of the mammalian radiation evolved, and neocortex often increased in size and the number of cortical areas, likely by the process of specializations within areas that subdivided areas. At least some areas, perhaps most, subdivided in another way by evolving two or more alternating types of small regions of different functional specializations, now referred to as cortical modules or columns. The specializations within and across cortical areas included those in the sizes of neurons and the extents of their processes, the dendrites and axons, and thus connections with other neurons. As a result, the neocortex of present-day mammals varies greatly within and across phylogenetically related groups (clades), while retaining basic features of organization from early ancestral mammals. In a number of present-day (extant) mammals, brains are relatively small and have little neocortex, with few areas and little structural differentiation, thus resembling early mammals. Other small mammals with little neocortex have specialized some part via selective enlargement and structural modifications to promote certain sensory abilities. Other mammals have a neocortex that is moderately to greatly expanded, with more cortical areas directly related to sensory processing and cognition and memory. The human brain is extreme in this way by having more neocortex in proportion to the rest of the brain, more cortical neurons, and likely more cortical areas.

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