Limits...
Procedural-based category learning in patients with Parkinson's disease: impact of category number and category continuity.

Filoteo JV, Maddox WT - Front Syst Neurosci (2014)

Bottom Line: Previously we found that Parkinson's disease (PD) patients are impaired in procedural-based category learning when category membership is defined by a nonlinear relationship between stimulus dimensions, but these same patients are normal when the rule is defined by a linear relationship (Maddox and Filoteo, 2001; Filoteo et al., 2005a,b).In the present study, we further examined the nature of PD patients' procedural-based deficit in two experiments designed to examine the impact of (1) the number of categories, and (2) category discontinuity on learning.Theoretically, this deficit might be related to dysfunctional communication among medium spiny neurons within the striatum, particularly given that these are cholinergic neurons and a cholinergic deficiency could underlie some of PD patients' cognitive impairment.

View Article: PubMed Central - PubMed

Affiliation: Veterans Administration San Diego Healthcare System San Diego, CA, USA ; Department of Psychiatry, University of California San Diego, CA, USA.

ABSTRACT
Previously we found that Parkinson's disease (PD) patients are impaired in procedural-based category learning when category membership is defined by a nonlinear relationship between stimulus dimensions, but these same patients are normal when the rule is defined by a linear relationship (Maddox and Filoteo, 2001; Filoteo et al., 2005a,b). We suggested that PD patients' impairment was due to a deficit in recruiting "striatal units" to represent complex nonlinear rules. In the present study, we further examined the nature of PD patients' procedural-based deficit in two experiments designed to examine the impact of (1) the number of categories, and (2) category discontinuity on learning. Results indicated that PD patients were impaired only under discontinuous category conditions but were normal when the number of categories was increased from two to four. The lack of impairment in the four-category condition suggests normal integrity of striatal medium spiny cells involved in procedural-based category learning. In contrast, and consistent with our previous observation of a nonlinear deficit, the finding that PD patients were impaired in the discontinuous condition suggests that these patients are impaired when they have to associate perceptually distinct exemplars with the same category. Theoretically, this deficit might be related to dysfunctional communication among medium spiny neurons within the striatum, particularly given that these are cholinergic neurons and a cholinergic deficiency could underlie some of PD patients' cognitive impairment.

No MeSH data available.


Related in: MedlinePlus

Stimulus distributions for the (A) Discontinuous and (B) Continuous conditions in Experiment 2. The solid line represents the optimal rule.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3928591&req=5

Figure 6: Stimulus distributions for the (A) Discontinuous and (B) Continuous conditions in Experiment 2. The solid line represents the optimal rule.

Mentions: The purpose of the current study is to examine both the “number of units” hypothesis and the “communication among units” hypothesis described above. Experiment 1 examined the ability of PD patients and normal controls (NC) to learn a procedural-based task in which there were either four categories (Four-Category condition) or two categories (Two-Category condition). Figure 4 displays the stimulus distributions for the Four- and Two-Category conditions. If PD results in a deficit in the number of hypothetical striatal units, then they should demonstrate greater impairment in the Four-Category condition as compared to the Two-Category condition. In contrast, Experiment 2 examined the “communication among units” hypothesis by determining the ability of PD patients and NC participants to learn categories that have either a discontinuous distribution of stimuli (Discontinuous condition) or a continuous distribution of stimuli (Continuous condition). Figure 6 displays the stimulus distributions for the Discontinuous and Continuous conditions. A finding that PD patients are impaired in the Discontinuous condition relative to the Continuous condition would provide theoretical support for the “communication among units” hypothesis of procedural-based category learning deficits in PD.


Procedural-based category learning in patients with Parkinson's disease: impact of category number and category continuity.

Filoteo JV, Maddox WT - Front Syst Neurosci (2014)

Stimulus distributions for the (A) Discontinuous and (B) Continuous conditions in Experiment 2. The solid line represents the optimal rule.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3928591&req=5

Figure 6: Stimulus distributions for the (A) Discontinuous and (B) Continuous conditions in Experiment 2. The solid line represents the optimal rule.
Mentions: The purpose of the current study is to examine both the “number of units” hypothesis and the “communication among units” hypothesis described above. Experiment 1 examined the ability of PD patients and normal controls (NC) to learn a procedural-based task in which there were either four categories (Four-Category condition) or two categories (Two-Category condition). Figure 4 displays the stimulus distributions for the Four- and Two-Category conditions. If PD results in a deficit in the number of hypothetical striatal units, then they should demonstrate greater impairment in the Four-Category condition as compared to the Two-Category condition. In contrast, Experiment 2 examined the “communication among units” hypothesis by determining the ability of PD patients and NC participants to learn categories that have either a discontinuous distribution of stimuli (Discontinuous condition) or a continuous distribution of stimuli (Continuous condition). Figure 6 displays the stimulus distributions for the Discontinuous and Continuous conditions. A finding that PD patients are impaired in the Discontinuous condition relative to the Continuous condition would provide theoretical support for the “communication among units” hypothesis of procedural-based category learning deficits in PD.

Bottom Line: Previously we found that Parkinson's disease (PD) patients are impaired in procedural-based category learning when category membership is defined by a nonlinear relationship between stimulus dimensions, but these same patients are normal when the rule is defined by a linear relationship (Maddox and Filoteo, 2001; Filoteo et al., 2005a,b).In the present study, we further examined the nature of PD patients' procedural-based deficit in two experiments designed to examine the impact of (1) the number of categories, and (2) category discontinuity on learning.Theoretically, this deficit might be related to dysfunctional communication among medium spiny neurons within the striatum, particularly given that these are cholinergic neurons and a cholinergic deficiency could underlie some of PD patients' cognitive impairment.

View Article: PubMed Central - PubMed

Affiliation: Veterans Administration San Diego Healthcare System San Diego, CA, USA ; Department of Psychiatry, University of California San Diego, CA, USA.

ABSTRACT
Previously we found that Parkinson's disease (PD) patients are impaired in procedural-based category learning when category membership is defined by a nonlinear relationship between stimulus dimensions, but these same patients are normal when the rule is defined by a linear relationship (Maddox and Filoteo, 2001; Filoteo et al., 2005a,b). We suggested that PD patients' impairment was due to a deficit in recruiting "striatal units" to represent complex nonlinear rules. In the present study, we further examined the nature of PD patients' procedural-based deficit in two experiments designed to examine the impact of (1) the number of categories, and (2) category discontinuity on learning. Results indicated that PD patients were impaired only under discontinuous category conditions but were normal when the number of categories was increased from two to four. The lack of impairment in the four-category condition suggests normal integrity of striatal medium spiny cells involved in procedural-based category learning. In contrast, and consistent with our previous observation of a nonlinear deficit, the finding that PD patients were impaired in the discontinuous condition suggests that these patients are impaired when they have to associate perceptually distinct exemplars with the same category. Theoretically, this deficit might be related to dysfunctional communication among medium spiny neurons within the striatum, particularly given that these are cholinergic neurons and a cholinergic deficiency could underlie some of PD patients' cognitive impairment.

No MeSH data available.


Related in: MedlinePlus