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THE FIRING OF PLACE CELLS IN THE DARK Anatomical location of Brocas area. Paul Broca Brains of Leborgne(top) and Lelong(bottom).

There are in the human mind a group of faculties and in the brain groups of convolutions, and the facts assembled by science so far allow to state, as I said before, that the great regions of the mind correspond to the great regions of the brain.

Egaz Moniz

Prefrontal Lobotomy Procedure(top),changes(bottom)

Normal psychic life depends upon the good functioning of brain synapses, and mental disorders appear as a result of synaptic derangements. Synaptic adjustments will then modify the corresponding ideas and force them into different channels. Using this approach we obtain cures and improvements but no failures.

Wilder Penfield

William Beecher Scoville Brenda Milner Penfield opines Cerebral Cortex to be the site of Implicit Memory.

H.M, the amnesiac we shall never forget sheds clues on memory, their distinction and location .

Hippocampus- Anatomy Rat Brain-Lateral View

Arrangement of Neurons In Hippocampus

The left and Right Hippocampi are dissimilar behaviorally. Left Right

Single-cell Recording in the Hippocampal Formation Reveals Two Major Classes of Units: Principal Cells and Theta Cells.

Okeefe and Ranck (1973) let rats explore a certain environment while they recorded activity of individual neurons in CA1 region known as Single Units.They noticed that there were two major classes of cells :complex-spike and theta cells.

Ranck had trained his animals to approach one location to obtain food and another to get water, and emphasized the relation of the complex- Spike cell firing pattern to the behavioral approach to reward. OKeefe was more impressed by the spatial correlate and named the cells place cells.

The second class of neurons, the theta cells, has less specific behavioral correlates. As the name implies, their behavioral correlates are closely related to those of the gross EEG waves and in particular theta.It is highly likely that in the rat the complex spike cells are pyramidal cells and the theta cells are one or more types of interneuron. Intracellular staining of neurons that display complex spikes in brain slices reveals they have the morphology of pyramidal cells, whereas those without complex spikes are interneurons.Complex-spike cells and theta cells have different physiological properties. A. Theta cells have a steady firing rate and constant size amplitude spikes, whereas C-S cells sometimes emit a complex-spike burst in which the later action potentials in the burst are lower in amplitude and broader.

*Firing field of a CA1 place cell. A. Raw data from a rat foraging for food in a square box for 10 minutes. Gray line traces the animals path through the environment; black boxes show firing of place cell. B. Place firing field as a grayscale map where darker colors represent higher firing rates. Inset number in white gives the peak firing rate(Source: The Hippocampus Book)Firing fields of 32 place cells simultaneously recorded while a rat foraged for food in a 62-cm2 box. The place field maps are arranged topographically so fields in the northwest of the box are located at the upper left, fields in the southwest are located at the lower left, and so on. In reality there is no topographical relation between the location of cells in the hippocampus and the location of their fields in an environment. (Source: The Hippocampus Book)

A place is defined as a location marked by no locallyperceptible cues and is therefore only recognizable relative toother perceptible landmarks or orienting gradients.

Long-Lasting Working Memories of Obstacles Established by Foreleg Stepping in Walking Cats Require Area 5 of the Posterior Parietal Cortex.David A. McVea,Andrew J. Taylor, andKeir G. Pearson.

Grid Cells and companions.Discovered in 2005 by May- Britt Moser and Edvard Moser when they ut it was unclear whether those place signals originated in the hippocampus itself or came from the outside. To address this question, we made intra-hippocampal lesions that disconnected the output stage of the circuit CA1 from the earlier stages. To our surprise, this did not abolish place coding in CA1.At first they noticed that many entorhinal cells spiked every time a rat went to a particular spot, like the place cells in the hippocampus. However, each cell had multiple firing locations and those firing locations formed a peculiarly regular pattern a hexagonal grid much like the arrangement of marbles in a Chinese checker board. Every cell did it this way, with actual firing locations differing between cells. The cells were organized topographically in the sense that the size of and distance between grid fields increased from dorsal to ventral.

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Source:Memory, navigation and theta rhythm in the hippocampal-entorhinal system. Buzsaki and E. Moser, 2013a) Stepwise increase of grid spacing at successive dorsoventral levels of medial entorhinal cortex. Spatial autocorrelograms for four example cells (one per dorsoventral module). (b) Remapping of hippocampal place cells in two environments. Top panels show responses of three grid cells to a change in the environment. Independent responses are illustrated by different degrees of rotation and translation. Bottom panels show inputs from the grid cells, each from a different module (purple, green and orange), at different locations in the environments. The three grid cells provide input to a particular CA3 cell (white spot at left) sufficient to cause it to fire when, and only when, the nodes of the three grids overlap. This occurs only at one location in this example. In the second environment, the altered coactivity of the grid cells activates a different subset of place cells at each location, and global remapping is observed in hippocampal place ensembles. Entorhinal cortex grid cells. Raw data (left) and firing fields (right)for three grid cells. Note the regularity ofthe firing, which forms a triangular gridpattern in each cell. Numbers indicate thepeak rate. Peaks of the three cells (topin grayscale, bottom as numbers 13)are slightly offset from each other so whensuperimposed they tend to tesselate thespace. (Source: After Hafting et al., 2005,by permission.

Four spatial cell types in the hippocampal formation.A. Place cell has single localizedfield and no directional selectivity. B. Place by directional cell hassingle localized field and strong directional selectivity. C. Headdirection cell does not have localized firing but has strong directionalselectivity. D. Grid cell has multiple place fields and no directional selectivity.Directional grid cells also exist. (Source: Edvard and May-Britt Moser.) Border cells express proximity to boundaries in a number of environmental configurations

The Firing of Hippocampal Place Cells in the Dark Depends on the Rats Recent Experience. Gregory J. Quirk, Robert U. Muller, and John L.Kubie, 1998.THE HERO

THE SETUP

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Four hippocampal place cells tested in the light-dark-light sequence. The 3 firing rate maps in each row correspond to the 3 segments of the L-D-L sequence. Cells A and B show strong persistence of spatial firing in the dark in the square and cylinder chambers, respectively. CellC weakly persisted, and cell D failed to persist. The persistence scores between the maps are as follows: cell A, Al:A2 = 0.57, Al:A3 = 0.68, A2:A3 = 0.83; cell& Bl:B2 = 0.58, Bl:B3 = 0.63, B2:B3 = 0.46; cell C, Cl:C2 = 0.34, Cl:C3 = 0.62, C2:C3 = 0.21; cell D, Dl:D2 = 0.13, Dl:D3= 0.20, D2:D3 = 0.08. Median firing rates of pixels are as follows (order: yellow, orange, red, green, blue, purple, in Hz.): cell A, 0.0, 0.69, 1.7 1,3.00, 6.49, 10.00; cell B, 0.0. 0.83, 2.86, 5.33, 9.14, 14.60; cell C, 0.0, 0.61, 2.50, 6.00, 11.61, 20.00; cell D, 0.0, 0.92, 2.22, 4.38, 7.32, 11.35.Histograms showing the distributions of the persistence scoresbetween the initial lighted segment and (A) the dark segment of theL-D-L sequence(B, ) the light segmenotf the L-D-L sequencea,n d( c)the dark segment of the D-L sequence. The triangle at 0.14 on theabscissa marks the cut-off for significance at the 0.001 level.

Three examples of cells whose firing patterns did not persist when the rat was placed directly into the darkened chamber.

Firing rate map for a lighted, 8 min recording session that was run subsequent to the D-L sequences for the cell shown in Figure 3C. This cell, which showed a firing field at 4 oclock in the cylinder in the L-D-L sequence, stopped firing when the rat was put into the darkened chamber (Fig. 3). The map above shows that the firing-field returned in a subsequent lighted session. Median rates of pixels are asfollows (order: yellow, orange, red, green, blue, purple, in Hz.): 0.0, 1 .0, 3.3, 6.2, 10.0, 13.8.

Spatial Firing of Hippocampal Place Cells in Blind Rats

Etienne Save, Arnaud Cressant, Catherine Thinus-Blanc, and Bruno Poucet Contrary to place cells in sighted rats, no cell in blind rats was observed to fire in the firing field if the rat had not made physical contact with an object previously.

In many cells recorded from blind rats, knowledge of one landmark position was enough to activate firing in the place field. This confirms that, to produce coherent firing, the hippocampal place cell system needs information about the location of objects. This result additionally suggests that the system is able to use the intrinsic (e.g., olfactory, tactile) properties of objects to recognize which object the animal has encountered.

Once landmark positions are known, the place cell system relies on the dynamic use of internally generated, motion-related information to update the position of the system throughout the environment.

Such information includes kinesthetic signals from the vestibular system, proprioceptive cues, and motor reference copy signals. Although motion-related signals are known to accumulate errors across successive movements in space, such errors can be corrected at each contact with an object by using the fixed object locations as a means for recalibrating a calculated position.

At any rate, our study suggests that the spatial impairments of blind animals, if any, are not the consequence of a decreased ability of the hippocampal place cell system to keep track of movements in space.

2008 Neuroscience Lecture 3 - Plan of Action: How the Spinal Cord Controls MovementHHMI/Thomas M. Jessell, Ph.D.HHMI's Holiday Lectures on Science"Plan of Action: How the Spinal Cord Controls Movement" by Thomas M. Jessell, Ph.D.Behavior involves movement. Movement drives simple respiratory programs to keep us breathing, as well as displays of emotiondesire, joy, remorsethat project our inner thoughts and moods. Understanding the workings of the neural circuits that control movement gives us a glimpse of how brain wiring and circuit activity control specific behaviors, including one of the more sophisticated aspects of human motor behaviorthe movement of our limbs. Consider baseball player Lou Gehrig's remarkable hand-eye coordination as he compiled one of baseball's most impressive hitting streaks, or the purity of cellist Jacqueline du Pr's tone as she played Haydn's Cello Concerto. Yet, both examples also remind us of the fragility of the motor system and its vulnerability to diseases: Gehrig succumbed to amyotrophic lateral sclerosis and du Pr to multiple sclerosis. Neural circuits in the spinal cord direct motor programs with impressive precision, ensuring that the many muscles in a limb are activated in precise temporal order. Sensory feedback systems report on the accuracy of motor programs, and signals from the brain permit us to change motor strategies moment by moment to accommodate an ever-changing world.Podcast2009-04-01T07:00:00Z1970-01-01 00:00:002008 Neuroscience Lecture 3 - Plan of Action: How the Spinal Cord Controls MovementHHMI/Thomas M. Jessell, Ph.D.HHMI's Holiday Lectures on Science"Plan of Action: How the Spinal Cord Controls Movement" by Thomas M. Jessell, Ph.D.Behavior involves movement. Movement drives simple respiratory programs to keep us breathing, as well as displays of emotiondesire, joy, remorsethat project our inner thoughts and moods. Understanding the workings of the neural circuits that control movement gives us a glimpse of how brain wiring and circuit activity control specific behaviors, including one of the more sophisticated aspects of human motor behaviorthe movement of our limbs. Consider baseball player Lou Gehrig's remarkable hand-eye coordination as he compiled one of baseball's most impressive hitting streaks, or the purity of cellist Jacqueline du Pr's tone as she played Haydn's Cello Concerto. Yet, both examples also remind us of the fragility of the motor system and its vulnerability to diseases: Gehrig succumbed to amyotrophic lateral sclerosis and du Pr to multiple sclerosis. Neural circuits in the spinal cord direct motor programs with impressive precision, ensuring that the many muscles in a limb are activated in precise temporal order. Sensory feedback systems report on the accuracy of motor programs, and signals from the brain permit us to change motor strategies moment by moment to accommodate an ever-changing world.Podcast2009-04-01T07:00:00Z1970-01-01 00:00:00