Reversible deactivation of motor cortex reveals that areas in parietal cortex are differentially dependent on motor cortex for the generation of movement.

Primates are characterized by specializations for manual manipulation, including expansion of posterior parietal cortex (PPC) and, in Catarrhines, evolution of a dexterous hand and opposable thumb. Previous studies examined functional interactions between motor cortex and PPC in New World monkeys and galagos, by inactivating M1 and evoking movements from PPC. These studies found that portions of PPC depend on M1 to generate movements.

The effects of prior exposure to prism lenses on de novo motor skill learning.

Motor learning involves plasticity in a network of brain areas across the cortex and cerebellum. Such traces of learning have the potential to affect subsequent learning of other tasks. In some cases, prior learning can interfere with subsequent learning, but it may be possible to potentiate learning of one task with a prior task if they are sufficiently different.

Coevolution of motor cortex and behavioral specializations associated with flight and echolocation in bats.

Bats have evolved behavioral specializations that are unique among mammals, including self-propelled flight and echolocation. However, areas of motor cortex that are critical in the generation and fine control of these unique behaviors have never been fully characterized in any bat species, despite the fact that bats compose ∼25% of extant mammalian species. Using intracortical microstimulation, we examined the organization of motor cortex in Egyptian fruit bats (Rousettus aegyptiacus), a species that has evolved a novel form of tongue-based echolocation.

Functional characterization of the fronto-parietal reaching and grasping network: reversible deactivation of M1 and areas 2, 5, and 7b in awake behaving monkeys.

In the present investigation, we examined the role of different cortical fields in the fronto-parietal reaching and grasping network in awake, behaving macaque monkeys. This network is greatly expanded in primates compared to other mammals and coevolved with glabrous hands with opposable thumbs and the extraordinary dexterous behaviors employed by a number of primates, including humans. To examine this, we reversibly deactivated the primary motor area (M1), anterior parietal area 2, and posterior parietal areas 5L and 7b individually while monkeys were performing two types of reaching and grasping tasks.

Distributed Motor Control of Limb Movements in Rat Motor and Somatosensory Cortex: The Sensorimotor Amalgam Revisited.

Which areas of the neocortex are involved in the control of movement, and how is motor cortex organized across species? Recent studies using long-train intracortical microstimulation demonstrate that in addition to M1, movements can be elicited from somatosensory regions in multiple species. In the rat, M1 hindlimb and forelimb movement representations have long been thought to overlap with somatosensory representations of the hindlimb and forelimb in S1, forming a partial sensorimotor amalgam. Here we use long-train intracortical microstimulation to characterize the movements elicited across frontal and parietal cortex.

The Multiple Representations of Complex Digit Movements in Primary Motor Cortex Form the Building Blocks for Complex Grip Types in Capuchin Monkeys.

In the present study, we investigated motor cortex (M1) and a small portion of premotor and parietal cortex using intracortical microstimulation in anesthetized capuchin monkeys. Capuchins are the only New World monkeys that have evolved an opposable thumb and use tools in the wild. Like most Old World monkeys and humans, capuchin monkeys have highly dexterous hands.

Cortical connections of area 2 and posterior parietal area 5 in macaque monkeys.

The overarching goal of the current investigation was to examine the connections of anterior parietal area 2 and the medial portion of posterior parietal area 5 in macaque monkeys; two areas that are part of a network involved reaching and grasping in primates. We injected neuroanatomical tracers into specified locations in each field and directly related labeled cells to histologically identified cortical field boundaries. Labeled cells were counted so that the relative density of projections to areas 2 and 5 from other cortical fields could be determined.

Representations of Fine Digit Movements in Posterior and Anterior Parietal Cortex Revealed Using Long-Train Intracortical Microstimulation in Macaque Monkeys.

The current investigation in macaque monkeys utilized long-train intracortical microstimulation to determine the extent of cortex from which movements could be evoked. Not only were movements evoked from motor areas (PMC and M1), but they were also evoked from posterior parietal (5, 7a, 7b) and anterior parietal areas (3b, 1, 2). Large representations of digit movements involving only the index finger (D2) and thumb (D1), were elicited from areas 1, 2, 7b, and M1.

Improved methods for acrylic-free implants in nonhuman primates for neuroscience research.

Traditionally, head fixation devices and recording cylinders have been implanted in nonhuman primates (NHP) using dental acrylic despite several shortcomings associated with acrylic. The use of more biocompatible materials such as titanium and PEEK is becoming more prevalent in NHP research. We describe a cost-effective set of procedures that maximizes the integration of headposts and recording cylinders with the animal's tissues while reducing surgery time.

Intracortical Microstimulation Maps of Motor, Somatosensory, and Posterior Parietal Cortex in Tree Shrews (Tupaia belangeri) Reveal Complex Movement Representations.

Long-train intracortical microstimulation (LT-ICMS) is a popular method for studying the organization of motor and posterior parietal cortex (PPC) in mammals. In primates, LT-ICMS evokes both multijoint and multiple-body-part movements in primary motor, premotor, and PPC. In rodents, LT-ICMS evokes complex movements of a single limb in motor cortex.

Noninvasive, in vivo imaging of subcortical mouse brain regions with 1.7 μm optical coherence tomography.

A spectral/Fourier domain optical coherence tomography (OCT) intravital microscope using a supercontinuum light source at 1.7 μm was developed to study subcortical structures noninvasively in the living mouse brain. The benefits of 1.

Reversible Deactivation of Motor Cortex Reveals Functional Connectivity with Posterior Parietal Cortex in the Prosimian Galago (Otolemur garnettii).

Unlabelled: We examined the functional macrocircuitry of frontoparietal networks in the neocortex of prosimian primates (Otolemur garnettii) using a microfluidic thermal regulator to reversibly deactivate selected regions of motor cortex (M1). During deactivation of either forelimb or mouth/face movement domains within M1, we used long-train intracortical microstimulation techniques to evoke movements from the rostral division of posterior parietal cortex (PPCr). We found that deactivation of M1 movement domains in most instances abolished movements evoked in PPCr.

Evolution of mammalian sensorimotor cortex: thalamic projections to parietal cortical areas in Monodelphis domestica.

The current experiments build upon previous studies designed to reveal the network of parietal cortical areas present in the common mammalian ancestor. Understanding this ancestral network is essential for highlighting the basic somatosensory circuitry present in all mammals, and how this basic plan was modified to generate species specific behaviors. Our animal model, the short-tailed opossum (Monodelphis domestica), is a South American marsupial that has been proposed to have a similar ecological niche and morphology to the earliest common mammalian ancestor.

Reversible deactivation of higher-order posterior parietal areas. I. Alterations of receptive field characteristics in early stages of neocortical processing.

Somatosensory processing in the anesthetized macaque monkey was examined by reversibly deactivating posterior parietal areas 5L and 7b and motor/premotor cortex (M1/PM) with microfluidic thermal regulators developed by our laboratories. We examined changes in receptive field size and configuration for neurons in areas 1 and 2 that occurred during and after cooling deactivation. Together the deactivated fields and areas 1 and 2 form part of a network for reaching and grasping in human and nonhuman primates.

Reversible deactivation of higher-order posterior parietal areas. II. Alterations in response properties of neurons in areas 1 and 2.

The role that posterior parietal (PPC) and motor cortices play in modulating neural responses in somatosensory areas 1 and 2 was examined with reversible deactivation by transient cooling. Multiunit recordings from neurons in areas 1 and 2 were collected from six anesthetized adult monkeys (Macaca mulatta) before, during, and after reversible deactivation of areas 5L or 7b or motor cortex (M1/PM), while select locations on the hand and forelimb were stimulated. Response changes were quantified as increases and decreases to stimulus-driven activity relative to baseline and analyzed during three recording epochs: during deactivation ("cool") and at two time points after deactivation ("rewarm 1," "rewarm 2").

A connection to the past: Monodelphis domestica provides insight into the organization and connectivity of the brains of early mammals.

The current experiment is one of a series of comparative studies in our laboratory designed to determine the network of somatosensory areas that are present in the neocortex of the mammalian common ancestor. Such knowledge is critical for appreciating the basic functional circuitry that all mammals possess and how this circuitry was modified to generate species-specific, sensory-mediated behavior. Our animal model, the gray short-tailed opossum (Monodelphis domestica), is a marsupial that is proposed to represent this ancestral state more closely than most other marsupials and, to some extent, even monotremes.

Fabrication of an inexpensive, implantable cooling device for reversible brain deactivation in animals ranging from rodents to primates.

We have developed a compact and lightweight microfluidic cooling device to reversibly deactivate one or more areas of the neocortex to examine its functional macrocircuitry as well as behavioral and cortical plasticity. The device, which we term the "cooling chip," consists of thin silicone tubing (through which chilled ethanol is circulated) embedded in mechanically compliant polydimethylsiloxane (PDMS). PDMS is tailored to compact device dimensions (as small as 21 mm(3)) that precisely accommodate the geometry of the targeted cortical area.

The functional organization and cortical connections of motor cortex in squirrels.

Despite extraordinary diversity in the rodent order, studies of motor cortex have been limited to only 2 species, rats and mice. Here, we examine the topographic organization of motor cortex in the Eastern gray squirrel (Sciurus carolinensis) and cortical connections of motor cortex in the California ground squirrel (Spermophilus beecheyi). We distinguish a primary motor area, M1, based on intracortical microstimulation (ICMS), myeloarchitecture, and patterns of connectivity.

All rodents are not the same: a modern synthesis of cortical organization.

Rodents are a major order of mammals that is highly diverse in distribution and lifestyle. Five suborders, 34 families, and 2,277 species within this order occupy a number of different niches and vary along several lifestyle dimensions such as diel pattern (diurnal vs. nocturnal), terrain niche, and diet.

Parallel evolution of cortical areas involved in skilled hand use.

Dexterous hands, used to manipulate food, tools, and other objects, are one of the hallmarks of primate evolution. However, the neural substrate of fine manual control necessary for these behaviors remains unclear. Here, we describe the functional organization of parietal cortical areas 2 and 5 in the cebus monkey.

Parieto-frontal interactions, personal space, and defensive behavior.

In the monkey brain, two interconnected cortical areas have distinctive neuronal responses to visual, tactile, and auditory stimuli. These areas are the ventral intraparietal area (VIP) and a polysensory zone in the precentral gyrus (PZ). The multimodal neurons in these areas typically respond to objects touching, near, or looming toward the body surface.

Parieto-frontal interactions, personal space, and defensive behavior.

In the monkey brain, two interconnected cortical areas have distinctive neuronal responses to visual, tactile, and auditory stimuli. These areas are the ventral intraparietal area (VIP) and a polysensory zone in the precentral gyrus (PZ). The multimodal neurons in these areas typically respond to objects touching, near, or looming toward the body surface.

Arm movements evoked by electrical stimulation in the motor cortex of monkeys.

Electrical stimulation of the motor cortex in monkeys can evoke complex, multijoint movements including movements of the arm and hand. In this study, we examined these movements in detail and tested whether they showed adaptability to differing circumstances such as to a weight added to the hand. Electrical microstimulation was applied to motor cortex using pulse trains of 500-ms duration (matching the approximate duration of a reach).

Super-flinchers and nerves of steel: defensive movements altered by chemical manipulation of a cortical motor area.

In a restricted zone of the monkey motor cortex, neurons respond to objects near, approaching, or touching the body. This polysensory zone was hypothesized to play a role in monitoring nearby stimuli for the guidance of defensive movements. To test this hypothesis, we chemically manipulated sites within that zone by injecting bicuculline (increasing neuronal activity) or muscimol (decreasing neuronal activity).