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Dynamic trajectory of multiple single-unit activity during working memory task in rats.

Zhang X, Yi H, Bai W, Tian X - Front Comput Neurosci (2015)

Bottom Line: The question raised here as to how the transient dynamics evolve in working memory.The approach worked by reconstructing state space from delays of the original single-unit firing rate variables, which were further analyzed using kernel principal component analysis (KPCA).Then the neural trajectories were obtained to visualize the multiple single-unit activity.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomedical Engineering, School of Biomedical Engineering and Technology, Tianjin Medical University Tianjin, China.

ABSTRACT
Working memory plays an important role in complex cognitive tasks. A popular theoretical view is that transient properties of neuronal dynamics underlie cognitive processing. The question raised here as to how the transient dynamics evolve in working memory. To address this issue, we investigated the multiple single-unit activity dynamics in rat medial prefrontal cortex (mPFC) during a Y-maze working memory task. The approach worked by reconstructing state space from delays of the original single-unit firing rate variables, which were further analyzed using kernel principal component analysis (KPCA). Then the neural trajectories were obtained to visualize the multiple single-unit activity. Furthermore, the maximal Lyapunov exponent (MLE) was calculated to quantitatively evaluate the neural trajectories during the working memory task. The results showed that the neuronal activity produced stable and reproducible neural trajectories in the correct trials while showed irregular trajectories in the incorrect trials, which may establish a link between the neurocognitive process and behavioral performance in working memory. The MLEs significantly increased during working memory in the correctly performed trials, indicating an increased divergence of the neural trajectories. In the incorrect trials, the MLEs were nearly zero and remained unchanged during the task. Taken together, the trial-specific neural trajectory provides an effective way to track the instantaneous state of the neuronal population during the working memory task and offers valuable insights into working memory function. The MLE describes the changes of neural dynamics in working memory and may reflect different neuronal population states in working memory.

No MeSH data available.


Diagram of rat working memory task on a Y-maze. The Y-maze apparatus have three identical plastic arms (same length) at a 120° angle from each other. A removable guillotine door is placed at the entrance and food pellets are placed in the food cribs at the end of the goal arms (Arm B and C). In the sample phase, the rat is placed at the start arm (Arm A). When the guillotine door is opened, the rat is free to enter either one of the goal arms to get a food reward. In the choice phase, the rat is rewarded for entering the arm that was not visited in the sample phase. The black solid line shows possible correct path, red dashed line shows possible incorrect path. The moments that the rat enters into the goal arm are detected by the infrared detector and marked by a red triangle (defined as the reference point).
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Figure 1: Diagram of rat working memory task on a Y-maze. The Y-maze apparatus have three identical plastic arms (same length) at a 120° angle from each other. A removable guillotine door is placed at the entrance and food pellets are placed in the food cribs at the end of the goal arms (Arm B and C). In the sample phase, the rat is placed at the start arm (Arm A). When the guillotine door is opened, the rat is free to enter either one of the goal arms to get a food reward. In the choice phase, the rat is rewarded for entering the arm that was not visited in the sample phase. The black solid line shows possible correct path, red dashed line shows possible incorrect path. The moments that the rat enters into the goal arm are detected by the infrared detector and marked by a red triangle (defined as the reference point).

Mentions: Male Sprague-Dawley rats weighing 300–350 g were placed on a reverse light cycle upon arrival and given ad libitum access to water with food restriction (2 h a day to retain at least 85% of normal body weight) for two consecutive days. Then the rats were familiarized with a Y-maze for two days. After habituation, the rats received daily training sessions (10 trials per day) on a working memory (delayed alternation) task. The Y maze consists of three gray, opaque plastic arms (length × width × height: 75 × 14.5 × 15 cm), at a 120° angle from each other. One arm is designated as the “start” arm and the other two arms are assigned to be the “goal” arms (Figure 1). The working memory task was described as follows (Goldman et al., 1971). At the beginning of a trial, the rat was placed on the end of the start arm (arm A). Each trial included two phases: a sample phase and a choice phase. In the sample phase, the rat could get some food in the crib as a reward when it arrived at the end of the goal arm (arm B or arm C). Then the rat returned to the start arm to make a free choice after a 5 s delay. In this choice phase, the rat received a food reward only if it entered the arm not visited in the sample phase. Consecutive visit to the same goal arm was defined as an error. Between trials, the arms were wiped with alcohol to remove potential olfactory cues. The occurrence of behavioral events indicating the rat turned into the goal arm was marked by an infrared sensor in the Y-maze and the corresponding time stamp was defined as the reference point.


Dynamic trajectory of multiple single-unit activity during working memory task in rats.

Zhang X, Yi H, Bai W, Tian X - Front Comput Neurosci (2015)

Diagram of rat working memory task on a Y-maze. The Y-maze apparatus have three identical plastic arms (same length) at a 120° angle from each other. A removable guillotine door is placed at the entrance and food pellets are placed in the food cribs at the end of the goal arms (Arm B and C). In the sample phase, the rat is placed at the start arm (Arm A). When the guillotine door is opened, the rat is free to enter either one of the goal arms to get a food reward. In the choice phase, the rat is rewarded for entering the arm that was not visited in the sample phase. The black solid line shows possible correct path, red dashed line shows possible incorrect path. The moments that the rat enters into the goal arm are detected by the infrared detector and marked by a red triangle (defined as the reference point).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4585230&req=5

Figure 1: Diagram of rat working memory task on a Y-maze. The Y-maze apparatus have three identical plastic arms (same length) at a 120° angle from each other. A removable guillotine door is placed at the entrance and food pellets are placed in the food cribs at the end of the goal arms (Arm B and C). In the sample phase, the rat is placed at the start arm (Arm A). When the guillotine door is opened, the rat is free to enter either one of the goal arms to get a food reward. In the choice phase, the rat is rewarded for entering the arm that was not visited in the sample phase. The black solid line shows possible correct path, red dashed line shows possible incorrect path. The moments that the rat enters into the goal arm are detected by the infrared detector and marked by a red triangle (defined as the reference point).
Mentions: Male Sprague-Dawley rats weighing 300–350 g were placed on a reverse light cycle upon arrival and given ad libitum access to water with food restriction (2 h a day to retain at least 85% of normal body weight) for two consecutive days. Then the rats were familiarized with a Y-maze for two days. After habituation, the rats received daily training sessions (10 trials per day) on a working memory (delayed alternation) task. The Y maze consists of three gray, opaque plastic arms (length × width × height: 75 × 14.5 × 15 cm), at a 120° angle from each other. One arm is designated as the “start” arm and the other two arms are assigned to be the “goal” arms (Figure 1). The working memory task was described as follows (Goldman et al., 1971). At the beginning of a trial, the rat was placed on the end of the start arm (arm A). Each trial included two phases: a sample phase and a choice phase. In the sample phase, the rat could get some food in the crib as a reward when it arrived at the end of the goal arm (arm B or arm C). Then the rat returned to the start arm to make a free choice after a 5 s delay. In this choice phase, the rat received a food reward only if it entered the arm not visited in the sample phase. Consecutive visit to the same goal arm was defined as an error. Between trials, the arms were wiped with alcohol to remove potential olfactory cues. The occurrence of behavioral events indicating the rat turned into the goal arm was marked by an infrared sensor in the Y-maze and the corresponding time stamp was defined as the reference point.

Bottom Line: The question raised here as to how the transient dynamics evolve in working memory.The approach worked by reconstructing state space from delays of the original single-unit firing rate variables, which were further analyzed using kernel principal component analysis (KPCA).Then the neural trajectories were obtained to visualize the multiple single-unit activity.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomedical Engineering, School of Biomedical Engineering and Technology, Tianjin Medical University Tianjin, China.

ABSTRACT
Working memory plays an important role in complex cognitive tasks. A popular theoretical view is that transient properties of neuronal dynamics underlie cognitive processing. The question raised here as to how the transient dynamics evolve in working memory. To address this issue, we investigated the multiple single-unit activity dynamics in rat medial prefrontal cortex (mPFC) during a Y-maze working memory task. The approach worked by reconstructing state space from delays of the original single-unit firing rate variables, which were further analyzed using kernel principal component analysis (KPCA). Then the neural trajectories were obtained to visualize the multiple single-unit activity. Furthermore, the maximal Lyapunov exponent (MLE) was calculated to quantitatively evaluate the neural trajectories during the working memory task. The results showed that the neuronal activity produced stable and reproducible neural trajectories in the correct trials while showed irregular trajectories in the incorrect trials, which may establish a link between the neurocognitive process and behavioral performance in working memory. The MLEs significantly increased during working memory in the correctly performed trials, indicating an increased divergence of the neural trajectories. In the incorrect trials, the MLEs were nearly zero and remained unchanged during the task. Taken together, the trial-specific neural trajectory provides an effective way to track the instantaneous state of the neuronal population during the working memory task and offers valuable insights into working memory function. The MLE describes the changes of neural dynamics in working memory and may reflect different neuronal population states in working memory.

No MeSH data available.