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International Journal of Molecular... Jul 2019Retinal ganglion cells (RGCs) extend axons out of the retina to transmit visual information to the brain. These connections are established during development through... (Review)
Review
Retinal ganglion cells (RGCs) extend axons out of the retina to transmit visual information to the brain. These connections are established during development through the navigation of RGC axons along a relatively long, stereotypical pathway. RGC axons exit the eye at the optic disc and extend along the optic nerves to the ventral midline of the brain, where the two nerves meet to form the optic chiasm. In animals with binocular vision, the axons face a choice at the optic chiasm-to cross the midline and project to targets on the contralateral side of the brain, or avoid crossing the midline and project to ipsilateral brain targets. Ipsilaterally and contralaterally projecting RGCs originate in disparate regions of the retina that relate to the extent of binocular overlap in the visual field. In humans virtually all RGC axons originating in temporal retina project ipsilaterally, whereas in mice, ipsilaterally projecting RGCs are confined to the peripheral ventrotemporal retina. This review will discuss recent advances in our understanding of the mechanisms regulating specification of ipsilateral versus contralateral RGCs, and the differential guidance of their axons at the optic chiasm. Recent insights into the establishment of congruent topographic maps in both brain hemispheres also will be discussed.
Topics: Animals; Axons; Brain; Cell Lineage; Humans; Retinal Ganglion Cells; Vision, Binocular; Visual Pathways
PubMed: 31277365
DOI: 10.3390/ijms20133282 -
The Journal of Neuroscience : the... Mar 2022Lateralization is a hallmark of somatosensory processing in the mammalian brain. However, in addition to their contralateral representation, unilateral tactile stimuli...
Lateralization is a hallmark of somatosensory processing in the mammalian brain. However, in addition to their contralateral representation, unilateral tactile stimuli also modulate neuronal activity in somatosensory cortices of the ipsilateral hemisphere. The cellular organization and functional role of these ipsilateral stimulus responses in awake somatosensory cortices, especially regarding stimulus coding, are unknown. Here, we targeted silicon probe recordings to the vibrissa region of primary (S1) and secondary (S2) somatosensory cortex of awake head-fixed mice of either sex while delivering ipsilateral and contralateral whisker stimuli. Ipsilateral stimuli drove larger and more reliable responses in S2 than in S1, and activated a larger fraction of stimulus-responsive neurons. Ipsilateral stimulus-responsive neurons were rare in layer 4 of S1, but were located in equal proportion across all layers in S2. Linear classifier analyses further revealed that decoding of the ipsilateral stimulus was more accurate in S2 than S1, whereas S1 decoded contralateral stimuli most accurately. These results reveal substantial encoding of ipsilateral stimuli in S1 and especially S2, consistent with the hypothesis that higher cortical areas may integrate tactile inputs across larger portions of space, spanning both sides of the body. Tactile information obtained by one side of the body is represented in the activity of neurons of the opposite brain hemisphere. However, unilateral tactile stimulation also modulates neuronal activity in the other, or ipsilateral, brain hemisphere. This ipsilateral activity may play an important role in the representation and processing of tactile information, in particular when the sense of touch involves both sides of the body. Our work in the whisker system of awake mice reveals that neocortical ipsilateral activity, in particular that of deep layer excitatory neurons of secondary somatosensory cortex (S2), contains information about the presence and the velocity of unilateral tactile stimuli, which supports a key role for S2 in integrating tactile information across both body sides.
Topics: Animals; Mammals; Mice; Somatosensory Cortex; Touch; Touch Perception; Vibrissae; Wakefulness
PubMed: 35135855
DOI: 10.1523/JNEUROSCI.1417-21.2022 -
Journal of Neuroscience Research Jun 2021Stroke-related damage to the crossed lateral corticospinal tract causes motor deficits in the contralateral (paretic) limb. To restore functional movement in the paretic... (Review)
Review
Stroke-related damage to the crossed lateral corticospinal tract causes motor deficits in the contralateral (paretic) limb. To restore functional movement in the paretic limb, the nervous system may increase its reliance on ipsilaterally descending motor pathways, including the uncrossed lateral corticospinal tract, the reticulospinal tract, the rubrospinal tract, and the vestibulospinal tract. Our knowledge about the role of these pathways for upper limb motor recovery is incomplete, and even less is known about the role of these pathways for lower limb motor recovery. Understanding the role of ipsilateral motor pathways to paretic lower limb movement and recovery after stroke may help improve our rehabilitative efforts and provide alternate solutions to address stroke-related impairments. These advances are important because walking and mobility impairments are major contributors to long-term disability after stroke, and improving walking is a high priority for individuals with stroke. This perspective highlights evidence regarding the contributions of ipsilateral motor pathways from the contralesional hemisphere and spinal interneuronal pathways for paretic lower limb movement and recovery. This perspective also identifies opportunities for future research to expand our knowledge about ipsilateral motor pathways and provides insights into how this information may be used to guide rehabilitation.
Topics: Efferent Pathways; Functional Laterality; Humans; Lower Extremity; Stroke; Stroke Rehabilitation
PubMed: 33665910
DOI: 10.1002/jnr.24822 -
Trends in Neurosciences Nov 2019Whereas voluntary movements have long been understood to derive primarily from the cortical hemisphere contralateral to a moving limb, substantial cortical activations... (Review)
Review
Whereas voluntary movements have long been understood to derive primarily from the cortical hemisphere contralateral to a moving limb, substantial cortical activations also occur in the same-sided, or ipsilateral, cortical hemisphere. These ipsilateral motor activations have recently been shown to be useful to decode specific movement features. Furthermore, in contrast to the classical understanding that unilateral limb movements are solely driven by the contralateral hemisphere, it appears that the ipsilateral hemisphere plays an active and specific role in the planning and execution of voluntary movements. Here we review the movement-related activations observed in the ipsilateral cortical hemisphere, interpret this evidence in light of the potential roles of the ipsilateral hemisphere in the planning and execution of movements, and describe the implications for clinical populations.
Topics: Animals; Biomechanical Phenomena; Extremities; Functional Laterality; Humans; Models, Neurological; Motor Activity; Motor Cortex; Movement; Neurons; Psychomotor Performance
PubMed: 31514976
DOI: 10.1016/j.tins.2019.08.008 -
The Journal of Invasive Cardiology Aug 2021This manuscript describes the refinements of ipsilateral wire protection and bailout strategy for large-bore femoral access and especially transcatheter aortic valve...
This manuscript describes the refinements of ipsilateral wire protection and bailout strategy for large-bore femoral access and especially transcatheter aortic valve replacement. This ipsilateral wire protection requires no additional expenses and can provide effective arteriotomy site protection without the need for contralateral femoral access, especially in cases when contralateral wiring and crossover are not feasible. Ipsilateral wiring can be done both as prophylactic protection and as bailout strategy. The exact steps required for ipsilateral protection and bailout are described. A comparison between ipsilateral wiring with conventional contralateral femoral and transradial wire protection is delineated.
Topics: Aortic Valve; Aortic Valve Stenosis; Femoral Artery; Humans; Transcatheter Aortic Valve Replacement; Treatment Outcome
PubMed: 34338655
DOI: No ID Found -
Frontiers in Bioengineering and... 2022This study aimed to characterize ipsilateral loading and return to weight-bearing symmetry (WBS) in patients undergoing total hip arthroplasty (THA) during activities of...
This study aimed to characterize ipsilateral loading and return to weight-bearing symmetry (WBS) in patients undergoing total hip arthroplasty (THA) during activities of daily living (ADLs) using instrumented insoles. A prospective study in 25 THA patients was performed, which included controlled pre- and postoperative follow-ups in a single rehabilitation center of an orthopedic department. Ipsilateral loading and WBS of ADLs were measured with insoles in THA patients and in a healthy control group of 25 participants. Measurements in the THA group were performed at 4 different visits: a week pre-THA, within a week post-THA, 3-6 weeks post-THA, and 6-12 weeks post-THA, whereas the healthy control group was measured once. ADLs included standing comfortably, standing evenly, walking, and sit-to-stand-to-sit (StS) transitions. All ADLs were analyzed using discrete methods, and walking included a time-scale analysis to provide temporal insights in the ipsilateral loading and WBS waveforms. THA patients only improved beyond their pre-surgery levels while standing comfortably (ipsilateral loading and WBS, < 0.05) and during StS transitions (WBS, < 0.05). Nevertheless, patients improved upon their ipsilateral loading and WBS deficits observed within a week post-surgery across all investigated ADLs. Ipsilateral loading and WBS of THA patients were comparable to healthy participants at 6-12 weeks post-THA, except for ipsilateral loading during walking ( < 0.05) at the initial and terminal double-leg support period of the stance phase. Taken together, insole measurements allow for the quantification of ipsilateral loading and WBS deficits during ADLs, identifying differences between pre- and postoperative periods, and differentiating THA patients from healthy participants. However, post-THA measurements that lack pre-surgery assessments may not be sensitive to identifying patient-specific improvements in ipsilateral loading and WBS. Moreover, StS transitions and earlier follow-up time points should be considered an important clinical metric of biomechanical recovery after THA.
PubMed: 35284427
DOI: 10.3389/fbioe.2022.813345 -
Anatomy & Cell Biology Mar 2020Neurotrophic keratitis is a rare corneal disease that is challenging to treat. Corneal neurotization (CN) is among the developing treatments that uses the supraorbital...
Neurotrophic keratitis is a rare corneal disease that is challenging to treat. Corneal neurotization (CN) is among the developing treatments that uses the supraorbital (SON) or supratrochlear (STN) nerve as a donor. Therefore, the goal of this study was to provide the detailed anatomy of these nerves and clarify their feasibility as donors for ipsilateral CN. Both sides of 10 fresh-frozen cadavers were used in this study, and the SON and STN were dissected using a microscope intra- and extraorbitally. The topographic data between the exit points of these nerves and the medial and lateral angle of the orbit were measured, and nerve rotation of these nerves toward the ipsilateral cornea were attempted. The SON and STN were found on 19 of 20 sides. The vertical and horizontal distances between the exit point of the SON and that of the STN, were 7.3±2.1 mm (vertical) and 4.5±2.3 mm, respectively. The mean linear distances between the medial angle and the exit points of each were 22.2±3.0 mm and 14.5±1.9 mm, respectively, and the mean linear distances between the lateral angle and the exit points of the SON and STN were 34.0±2.7 mm and 36.9±2.5 mm, respectively. These nerves rotated ipsilaterally toward the center of the orbit easily. A better understanding of the anatomy of these nerves can contribute to the development and improvement of ipsilateral CN.
PubMed: 32274242
DOI: 10.5115/acb.19.147 -
Physiological Research Dec 2022Arterial blood to the human uterus is provided by a pair of uterine arteries (UA) and supported by terminal branches of ovarian (OA) and vaginal arteries (VA)....
Arterial blood to the human uterus is provided by a pair of uterine arteries (UA) and supported by terminal branches of ovarian (OA) and vaginal arteries (VA). Literature reports the existence of ipsilateral and contralateral anastomoses between these arteries and the UA, but data on the prevalence of such anastomoses are discrepant. The aim of this trial is to study whether contralateral and ipsilateral anastomoses exist. We studied nine human uterine specimens, which were obtained from (i) human cadavers (n = 6), (ii) uterine transplant recipients (n = 2), and (iii) one altruistic uterine donor (n = 1). We injected India ink into the graft through the UA of each specimen (n = 8) or OA (n = 1). We semiquantitatively observed and evaluated the extent of the injection on horizontal, vertical, and transmural levels. The dye permeated beyond the midline in 9/9 (100 %) cases. Near-complete/complete permeation to the contralateral side was observed in 6/9 (66 %) cases. The dye permeated ipsilaterally throughout all uterine levels in 8/8 cases (100 %) of UA injection. The entire wall of the myometrium was permeated in 2/9 (22 %) cases. In 7/9 (78 %) cases, the wall of the myometrium was permeated less than halfway through. In conclusion, the preliminary results of this study prove the existence of ipsilateral and contralateral anastomoses. Complete transmural injection was observed in only 22 % of cases; however, this finding does not provide information about the functional capacity of these anastomoses. More data and studies are necessary to make definitive conclusions.
Topics: Female; Humans; Uterus; Ovary; Arteries; Pelvis; Regional Blood Flow
PubMed: 36592444
DOI: 10.33549/physiolres.934972