Neurons In Parietal Cortex Research Articles

CHANGES IN THE CEREBRAL CORTEX NEURON ULTRASTRUCTURE IN RATS WITH PARTIAL CEREBRAL ISCHEMIA

The ultrastructural characteristics of neuronal organelles are significant indicators of brain damage under ischemic exposure, which necessitates the study of changes in the ultrastructure of brain neurons.
 The aim of the study was to examine the disorders of brain neurons under its partial ischemia at the ultrastructural level using an experimental model.
 Materials and Methods. The experimental group included 12 male rats weighing 260±20 g, the control group consisted of 6 falsely operated male rats of the same weight. Partial cerebral ischemia (PCI) was modeled by right common carotid artery ligation. The material was taken 1 hour after the operation.
 Results. The study showed that the size and shape of the mitochondria of neurons of the parietal cortex and the hippocampus in PCI rats did not differ from those of the control group (p>0.05), except for a smaller number of cristae per unit area in the mitochondria of parietal cortex neurons (by 18 %, p<0.05).
 The size and shape of the Golgi complex and lysosomes did not differ in the groups either. However, there was an increase in the number of free ribosomes in the cytoplasm of neurons in the parietal cortex and hippocampus of PCI rats, by 58 % and 54 %, respectively (p<0.05).
 The ratio of fixed and free ribosomes in control rats decreased from 3.4 to 0.8 in the parietal cortex (p<0.05) and from 2.33 to 0.7 in the hippocampus (p<0.05).
 Conclusions. In general, the neuron ultrastructure in PCI rats was similar to that in the control group, which might be due to blood flow compensation in the circle of Willis. An increase in the number of free ribosomes is a sign of deranged protein biosynthesis in neurons. A decrease in the number of mitochondrial cristae in neurons in the parietal cortex indicates energy deficiency.

Shared Neural Activity But Distinct Neural Dynamics for Cognitive Control in Monkey Prefrontal and Parietal Cortex.

To better understand how prefrontal networks mediate forms of cognitive control disrupted in schizophrenia, we translated a variant of the AX continuous performance task that measures specific deficits in the human disease to 2 male monkeys and recorded neurons in PFC and parietal cortex during task performance. In the task, contextual information instructed by cue stimuli determines the response required to a subsequent probe stimulus. We found parietal neurons encoding the behavioral context instructed by cues that exhibited nearly identical activity to their prefrontal counterparts (Blackman et al., 2016). This neural population switched their preference for stimuli over the course of the trial depending on whether the stimuli signaled the need to engage cognitive control to override a prepotent response. Cues evoked visual responses that appeared in parietal neurons first, whereas population activity encoding contextual information instructed by cues was stronger and more persistent in PFC. Increasing cognitive control demand biased the representation of contextual information toward the PFC and augmented the temporal correlation of task-defined information encoded by neurons in the two areas. Oscillatory dynamics in local field potentials differed between cortical areas and carried as much information about task conditions as spike rates. We found that, at the single-neuron level, patterns of activity evoked by the task were nearly identical between the two cortical areas. Nonetheless, distinct population dynamics in PFC and parietal cortex were evident. suggesting differential contributions to cognitive control.SIGNIFICANCE STATEMENT We recorded neural activity in PFC and parietal cortex of monkeys performing a task that measures cognitive control deficits in schizophrenia. This allowed us to characterize computations performed by neurons in the two areas to support forms of cognitive control disrupted in the disease. Subpopulations of neurons in the two areas exhibited parallel modulations in firing rate; and as a result, all patterns of task-evoked activity were distributed between PFC and parietal cortex. This included the presence in both cortical areas of neurons reflecting proactive and reactive cognitive control dissociated from stimuli or responses in the task. However, differences in the timing, strength, synchrony, and correlation of information encoded by neural activity were evident, indicating differential contributions to cognitive control.

Low-dimensional encoding of decisions in parietal cortex reflects long-term training history

Neurons in parietal cortex exhibit task-related activity during decision-making tasks. However, it remains unclear how long-term training to perform different tasks over months or even years shapes neural computations and representations. We examine lateral intraparietal area (LIP) responses during a visual motion delayed-match-to-category task. We consider two pairs of male macaque monkeys with different training histories: one trained only on the categorization task, and another first trained to perform fine motion-direction discrimination (i.e., pretrained). We introduce a novel analytical approach—generalized multilinear models—to quantify low-dimensional, task-relevant components in population activity. During the categorization task, we found stronger cosine-like motion-direction tuning in the pretrained monkeys than in the category-only monkeys, and that the pretrained monkeys’ performance depended more heavily on fine discrimination between sample and test stimuli. These results suggest that sensory representations in LIP depend on the sequence of tasks that the animals have learned, underscoring the importance of considering training history in studies with complex behavioral tasks.

Transformation of acoustic information to sensory decision variables in the parietal cortex

The process by which sensory evidence contributes to perceptual choices requires an understanding of its transformation into decision variables. Here, we address this issue by evaluating the neural representation of acoustic information in the auditory cortex-recipient parietal cortex, while gerbils either performed a two-alternative forced-choice auditory discrimination task or while they passively listened to identical acoustic stimuli. During task engagement, stimulus identity decoding performance from simultaneously recorded parietal neurons significantly correlated with psychometric sensitivity. In contrast, decoding performance during passive listening was significantly reduced. Principal component and geometric analyses revealed the emergence of low-dimensional encoding of linearly separable manifolds with respect to stimulus identity and decision, but only during task engagement. These findings confirm that the parietal cortex mediates a transition of acoustic representations into decision-related variables. Finally, using a clustering analysis, we identified three functionally distinct subpopulations of neurons that each encoded task-relevant information during separate temporal segments of a trial. Taken together, our findings demonstrate how parietal cortex neurons integrate and transform encoded auditory information to guide sound-driven perceptual decisions.

Task specificity in mouse parietal cortex

Parietal cortex is implicated in a variety of behavioral processes, but it is unknown whether and how its individual neurons participate in multiple tasks. We trained head-fixed mice to perform two visual decision tasks involving a steering wheel or a virtual T-maze and recorded from the same parietal neurons during these two tasks. Neurons that were active during the T-maze task were typically inactive during the steering-wheel task and vice versa. Recording from the same neurons in the same apparatus without task stimuli yielded the same specificity as in the task, suggesting that task specificity depends on physical context. To confirm this, we trained some mice in a third task combining the steering wheel context with the visual environment of the T-maze. This hybrid task engaged the same neurons as those engaged in the steering-wheel task. Thus, participation by neurons in mouse parietal cortex is task specific, and this specificity is determined by physical context.

Robust Coding of Eye Position in Posterior Parietal Cortex despite Context-Dependent Tuning.

Neurons in posterior parietal cortex (PPC) encode many aspects of the sensory world (e.g., scene structure), the posture of the body, and plans for action. For a downstream computation, however, only some of these dimensions are relevant; the rest are "nuisance variables" because their influence on neural activity changes with sensory and behavioral context, potentially corrupting the read-out of relevant information. Here we show that a key postural variable for vision (eye position) is represented robustly in male macaque PPC across a range of contexts, although the tuning of single neurons depended strongly on context. Contexts were defined by different stages of a visually guided reaching task, including (1) a visually sparse epoch, (2) a visually rich epoch, (3) a "go" epoch in which the reach was cued, and (4) during the reach itself. Eye position was constant within trials but varied across trials in a 3 × 3 grid spanning 24° × 24°. Using demixed principal component analysis of neural spike-counts, we found that the subspace of the population response encoding eye position is orthogonal to that encoding task context. Accordingly, a context-naive (fixed-parameter) decoder was nevertheless able to estimate eye position reliably across contexts. Errors were small given the sample size (∼1.78°) and would likely be even smaller with larger populations. Moreover, they were comparable to that of decoders that were optimized for each context. Our results suggest that population codes in PPC shield encoded signals from crosstalk to support robust sensorimotor transformations across contexts.SIGNIFICANCE STATEMENT Neurons in posterior parietal cortex (PPC) which are sensitive to gaze direction are thought to play a key role in spatial perception and behavior (e.g., reaching, navigation), and provide a potential substrate for brain-controlled prosthetics. Many, however, change their tuning under different sensory and behavioral contexts, raising the prospect that they provide unreliable representations of egocentric space. Here, we analyze the structure of encoding dimensions for gaze direction and context in PPC during different stages of a visually guided reaching task. We use demixed dimensionality reduction and decoding techniques to show that the coding of gaze direction in PPC is mostly invariant to context. This suggests that PPC can provide reliable spatial information across sensory and behavioral contexts.

Adaptive integration of self-motion and goals in posterior parietal cortex.

SUMMARYRats readily switch between foraging and more complex navigational behaviors such as pursuit of other rats or prey. These tasks require vastly different tracking of multiple behaviorally significant variables including self-motion state. To explore whether navigational context modulates self-motion tracking, we examined self-motion tuning in posterior parietal cortex neurons during foraging versus visual target pursuit. Animals performing the pursuit task demonstrate predictive processing of target trajectories by anticipating and intercepting them. Relative to foraging, pursuit yields multiplicative gain modulation of self-motion tuning and enhances self-motion state decoding. Self-motion sensitivity in parietal cortex neurons is, on average, history dependent regardless of behavioral context, but the temporal window of self-motion integration extends during target pursuit. Finally, many self-motion-sensitive neurons conjunctively track the visual target position relative to the animal. Thus, posterior parietal cortex functions to integrate the location of navigationally relevant target stimuli into an ongoing representation of past, present, and future locomotor trajectories.

Cortical and hippocampal dynamics under logical fragmentation of environmental space

Navigation is often constrained to pathways, and a recurring problem concerns whether to turn left or right when approaching an intersection. We examined this problem during T-maze performance in which the maze location in the recording environment varied over five-trial blocks and analyzed the associated positional firing patterns of hippocampal CA1 and posterior parietal cortex neurons. An arbitrary partitioning of the environmental space determined the left versus right turning rule for T-maze behavior. Under these conditions, rats learned the logical fragmentation of allocentric space into left turn and right turn sub-regions. Paradoxically, under these conditions, the spatial tuning of both posterior parietal cortex and hippocampal CA1 neurons followed the frame of reference given by the T-maze, as opposed to the location in the environment. Moreover, first trials within each block were associated with distinct firing rate changes for both posterior parietal cortex and hippocampal CA1 neurons. These data support a model where spatial tuning by hippocampus and cortex can interact to guide choice behavior in complex, path-based environments where a correct turn choice varies across environmental locations, and as a function of recent experience.

Transformation of acoustic information to sensory decisions in parietal cortex

Integrating sensory information over time is fundamental for guiding perceptual decisions. This process is facilitated by the transformation of stimulus representations downstream of sensory cortex. Here, we ask how the neural representations of auditory information are transformed in the auditory-recipient parietal cortex, a region that is causally associated with sound-driven perceptual decisions. Wireless recordings of neural activity were conducted in parietal cortex while gerbils performed an alternative forced-choice (AFC) auditory temporal integration task. Gerbils were required to discriminate amplitude modulated (AM) noise at 4 vs 10 Hz across various signal durations (100–2000 ms). Task performance was poor at short AM durations (100–300 ms), improved with longer durations, and reached an optimum at ≥600 ms. During task performance, individual neurons displayed a rise in firing rate that peaked prior to the animals’ decision. Population activity from simultaneously recorded parietal cortex neurons was strongly correlated with behavior outcomes, leaving open whether parietal representation was purely motor-related or included a sensory component. Thus, we evaluated population activity during disengaged sessions, and found a representation of the acoustic stimulus. Our findings suggest that parietal cortex neurons represent both the acoustic stimulus and sound-driven decision, demonstrating the progression of auditory processing downstream of auditory cortex.

Motor Activity and Levels of Expression of mRNA for the Proteins NAP-22 and GAP-43 in Spontaneously Hypertensive Rats

The aim of the present work was to identify differences in movement activity in SHR and WKY rats and to assess the levels of expression of mRNA for NAP-22 and GAP-43 proteins in neurons in the parietal cortex and hippocampus. Movement activity in SHR and WKY rats (four animals in each group) was measured using a telemetric method over three days. Levels of expression of mRNA for NAP-22 and GAP-43 proteins in parietal cortex and hippocampal neurons in further groups of rats of the same strains (10 animals in each group) were measured in real time by PCR. Studies were carried out using animals from the Biological Collection of the Institute of Physiology, Russian Academy of Sciences. Movement activity in SHR rats was greater than that in WKY rats, though statistically these differences were significant only during the dark phase. Expression levels of mRNA for NAP-22 and GAP-43 proteins in SHR rats were lower than those in WKY rats in both the parietal cortex and the hippocampus. These results lead to the conclusion that the greater mobility in SHR rats reflects the typical hyperactivity of rats of this line, making them a suitable model for attention deficit hyperactivity disorder. Changes in the expression levels of mRNA for NAP-22 and GAP-43 proteins may be linked with behavioral impairments.

A shared neural substrate for action verbs and observed actions in human posterior parietal cortex.

High-level sensory and motor cortical areas are activated when processing the meaning of language, but it is unknown whether, and how, words share a neural substrate with corresponding sensorimotor representations. We recorded from single neurons in human posterior parietal cortex (PPC) while participants viewed action verbs and corresponding action videos from multiple views. We find that PPC neurons exhibit a common neural substrate for action verbs and observed actions. Further, videos were encoded with mixtures of invariant and idiosyncratic responses across views. Action verbs elicited selective responses from a fraction of these invariant and idiosyncratic neurons, without preference, thus associating with a statistical sampling of the diverse sensory representations related to the corresponding action concept. Controls indicated that the results are not the product of visual imagery or arbitrary learned associations. Our results suggest that language may activate the consolidated visual experience of the reader.

Approximate number representations emerge in object-trained convolutional neural networks and show human-like signatures of number discrimination

What are the visual input analyzers that yield numerosity representations? Recent work from Nasr et al. (2019) provides an interesting possibility: numerosity representations are implemented by the same cortical networks that can classify objects. They found that a convolutional neural network trained on object classification had units with tuning curves for numerosity, similar to neurons in primate parietal and frontal cortex. Here, we extend these findings, examining whether the neural network’s number representations are tolerant to stimulus variation and show signatures of human number perception. We recorded responses to dot displays in each unit of AlexNet trained on 1000-way object classification. A subset of units in AlexNet had gaussian tuning curves for number, with wider tuning curves for higher preferred numerosities. Tuning curves were stable across stimulus sets controlling for surface area, density, convex hull, total circumference, and dot radius. Extending previous findings, we also observed that the tuning curves were even maintained in textured dot displays (for example, fur-textured dots on grass-textured background). These results were replicated in another architecture (VGG16) and critically were not evident in an untrained network. Next, we tested whether AlexNet’s number tuning was susceptible to grouping effects similar to the human visual system. Both humans and AlexNet underestimated the numerosity of displays with dots grouped into pairs relative to displays with randomly arranged dots. We also created images in which lines connected pairs of dots, decreasing the number of continuous objects. Like humans, AlexNet’s number representations decreased as dots were connected. Altogether, these results indicate that neural networks trained on object recognition gain robust number representations. Moreover, these representations are influenced by spatial grouping and connectedness, matching properties of human behavior. These results support the view that the same input analyzers that untangle object categories from retinal input also yield approximate number representations.

Decoding of standard and non-standard visuomotor associations from parietal cortex

Objective. Neural signals can be decoded and used to move neural prostheses with the purpose of restoring motor function in patients with mobility impairments. Such patients typically have intact eye movement control and visual function, suggesting that cortical visuospatial signals could be used to guide external devices. Neurons in parietal cortex mediate sensory-motor transformations, encode the spatial coordinates for reaching goals, hand position and movements, and other spatial variables. We studied how spatial information is represented at the population level, and the possibility to decode not only the position of visual targets and the plans to reach them, but also conditional, non-spatial motor responses. Approach. The animals first fixated one of nine targets in 3D space and then, after the target changed color, either reached toward it, or performed a non-spatial motor response (lift hand from a button). Spiking activity of parietal neurons was recorded in monkeys during two tasks. We then decoded different task related parameters. Main results. We first show that a maximum-likelihood estimation (MLE) algorithm trained separately in each task transformed neural activity into accurate metric predictions of target location. Furthermore, by combining MLE with a Naïve Bayes classifier, we decoded the monkey’s motor intention (reach or hand lift) and the different phases of the tasks. These results show that, although V6A encodes the spatial location of a target during a delay period, the signals they carry are updated around the movement execution in an intention/motor specific way. Significance. These findings show the presence of multiple levels of information in parietal cortex that could be decoded and used in brain machine interfaces to control both goal-directed movements and more cognitive visuomotor associations.

Radiation-Induced Changes in Protein Content in the Brain Neurons

The aim of research was to study radiation-induced changes in the protein content in the brain neurons after exposure to small doses of ionizing radiation. Material and methods. The study was performed in compliance with the rules of bioethics. The study included 300 male rats, aged 4 months at the beginning of the experiment, that were exposed to radiation in total doses of 0.1; 0.2; 0.5 and 1 Gy given as a single dose or fractionated (equal portions for 5 days with a dose rate of 0.5 and 6.6 Gy/h). Morphometric and tinctorial parameters of neurons and the dynamics of protein content in the brain neurons over the entire life span of animals were assessed using neuromorphological methods. The results obtained were statistically processed using software packages Statistica 6.1, which included parametric criteria and mathematical modeling. Results . In animals of the control group and in animals exposed to radiation wave-like changes in the protein content in the brain neurons occurred during the whole life; in animals exposed to irradiation parameters of these changes gradually decreased by the end of the irradiation period. Regression analysis showed that irradiation in the studied doses had a nonlinear stochastic effect on the protein content in neurons, had no dose-time dependence and did not result in significant organic changes in the brain neurons. At the end of the experiment, with the death of both irradiated and control animals, the protein content in neurons was statistically significantly reduced in all groups, but to a greater extent in irradiated animals. Moreover, the greatest decrease in protein content was observed in the pear-shaped neurons of the cerebellar cortex, and the parietal cortex neurons were more resistant to the radiation factor in terms of protein content. Conclusion. No significant radiation-induced changes in the content and topochemistry of histochemical reaction products were revealed when detecting protein in the structures of brain neurons. At the end of the experiment, the protein content in the neurons of the parietal cortex of the irradiated animals practically correlated to that in animals of age control, and was statistically significantly reduced in other parts of the brain.

Flexible coding of object motion in multiple reference frames by parietal cortex neurons.

Neurons represent spatial information in diverse reference frames, but it remains unclear whether neural reference frames change with task demands and whether these changes can account for behavior. We examined how neurons represent the direction of a moving object during self-motion, while monkeys switched, from trial to trial, between reporting object direction in head- and world-centered reference frames. Self-motion information is needed to compute object motion in world coordinates, but should be ignored when judging object motion in head coordinates. Neural responses in the ventral intraparietal area are modulated by the task reference frame, such that population activity represents object direction in either reference frame. In contrast, responses in the lateral portion of the medial superior temporal area primarily represent object motion in head coordinates. Our findings demonstrate a neural representation of object motion that changes with task requirements.

Learned Representation of Implied Serial Order in Posterior Parietal Cortex

Monkeys can learn the implied ranking of pairs of images drawn from an ordered set, despite never seeing all of the images simultaneously and without explicit spatial or temporal cues. We recorded the activity of posterior parietal cortex (including lateral intraparietal area LIP) neurons while monkeys learned 7-item transitive inference (TI) lists with 2 items presented on each trial. Behavior and neuronal activity were significantly influenced by the ordinal relationship of the stimulus pairs, specifically symbolic distance (the difference in rank) and joint rank (the sum of the ranks). Symbolic distance strongly predicted decision accuracy and learning rate. An effect of joint rank on performance was found nested within the symbolic distance effect. Across the population of neurons, there was significant modulation of firing correlated with the relative ranks of the two stimuli presented on each trial. Neurons exhibited selectivity for stimulus rank during learning, but not before or after. The observed behavior is poorly explained by associative or reward mechanisms, and appears more consistent with a mental workspace model in which implied serial order is mapped within a spatial framework. The neural data suggest that posterior parietal cortex supports serial learning by representing information about the ordinal relationship of the stimuli presented during a given trial.

Neural coding of action in three dimensions: Task- and time-invariant reference frames for visuospatial and motor-related activity in parietal area V6A.

Goal-directed movements involve a series of neural computations that compare the sensory representations of goal location and effector position, and transform these into motor commands. Neurons in posterior parietal cortex (PPC) control several effectors (e.g., eye, hand, foot) and encode goal location in a variety of spatial coordinate systems, including those anchored to gaze direction, and to the positions of the head, shoulder, or hand. However, there is little evidence on whether reference frames depend also on the effector and/or type of motor response. We addressed this issue in macaque PPC area V6A, where previous reports using a fixate-to-reach in depth task, from different starting arm positions, indicated that most units use mixed body/hand-centered coordinates. Here, we applied singular value decomposition and gradient analyses to characterize the reference frames in V6A while the animals, instead of arm reaching, performed a nonspatial motor response (hand lift). We found that most neurons used mixed body/hand coordinates, instead of "pure" body-, or hand-centered coordinates. During the task progress the effect of hand position on activity became stronger compared to target location. Activity consistent with body-centered coding was present only in a subset of neurons active early in the task. Applying the same analyses to a population of V6A neurons recorded during the fixate-to-reach task yielded similar results. These findings suggest that V6A neurons use consistent reference frames between spatial and nonspatial motor responses, a functional property that may allow the integration of spatial awareness and movement control.

HISTOLOGICAL VIOLATIONS IN THE RAT HIPPOCAMPUS AND PARIETAL CORTEX IN TOTAL CEREBRAL ISCHEMIA

Objective. To analyze the changes in the size and shape of perikaryons and the degree of cytoplasm chromatophilia of the rat hippocampal and parietal cortex neurons at different periods after the modeling of total cerebral ischemia. Material and Methods. The experiments were performed on 42 male outbred white rats with an initial weight of 240 ± 20 g. Total cerebral ischemia in white outbred rats was modeled by decapitation. The material for further histological examination was taken at the 1st, 5th, 15th, 30th and 60th minutes, as well as 5 and 24 hours after decapitation. The study of histological preparations was carried out using an Axioscop 2 plus microscope, a digital video camera and the ImageWarp image analysis program. Among the total number, the cells were isolated by the intensity of cytoplasm staining (chromatophilia). After a preliminary check for the normal distribution of indicators, the data obtained were analyzed by non-parametric statistics. Results. With total cerebral ischemia, a decrease in the size of neurons and deformation of perikaryons were observed. Normochromic neurons completely disappeared at the 60th minute. The number of hyperchromic neurons increased, and then progressively decreased. Shrunken neurons made up the majority of cells in the studied cortical sections at the 30–60th minutes, and then, after 5 and 24 hours, cells with pericellular edema prevailed in the neuron population.Conclusion. The obtained data on histological changes in neurons of phylogenetically different parts of the cerebral cortex in the dynamics of total cerebral ischemia provide the basis for further detailed study of post-mortem changes of the brain as well as determining the time of death, thus creating a fundamental basis for studying the properties of neurons, including their transition from one functional state to another.

Neural effects of continuous theta-burst stimulation on single neurons in macaque parietal cortex

Theta-burst transcranial magnetic stimulation (TBS) has recently received much interest because it can be used to up- or downregulate brain activity non-invasively. However, its behavioral effects are highly variable. A better understanding of TBS influence on different neuronal populations is currently needed to improve its reproducibility. We showed that single-pulse TMS (120% of resting motor threshold) induces a short-latency burst of action potentials lasting 80 ms (Romero et al., Soc Neurosci 2016). Here, we measured the after-effects of continuous TBS (cTBS, 300 pulses) on the TMS-induced burst and spontaneous neuronal activity in macaque parietal cortex during passive fixation. We first searched for well isolated single neurons, and recorded stable TMS-evoked bursts before cTBS. Next, we applied cTBS, and immediately resumed the single-pulse TMS protocol to assess changes in excitability up to 50 minutes post-cTBS. cTBS caused a reduction in spontaneous activity (31%, p < 0.001) and a robust reduction (29%, p

Effects of Experemental Cerebral Ishemia on Metabolic Characteristics of Parietal Cortex Neurons

The aim of the paper was to estimate the effect of experimental cerebral ischemia on metabolic characteristics of parietal cortex neurons. The experiments were carried out on 12 laboratory male rats. Cerebral ischemia was modeled with bilateral joint carotid arteries with durations of 60 minutes under intravenous thiopental anesthesia (40-50 mg / kg). The rats were decapitated and the samples of the brain parietal cortex were prepared for histological and histochemical examination in combination with morphometry to examine the 5 th layer inner pyramidal neurons. It was increased the number of pathological forms and shrinkage of the 5 th layer inner pyramidal neurons after cerebral ischemia in rats. The histochemical examination was revealed the inhibition of NADH-, glucose-6-phosphate dehydrogenase and succinate dehydrogenases as well as activation of lactate dehydrogenase and acid phosphatase. Cerebral ischemia induces deep histological and histochemical changes in the parietal cortex neurons in rats, including shrinkage of parietal cortex neurons and disturbances of their energy metabolism.