Rule-based And Information-integration Category Learning In Bipolar Disorder Patients

Classification is an aspect of human cognition that affects all aspects of our lives.At present,many researches show that there are two independent systems in the category learning.The multiple-systems theory holds that rule-based(RB)and information-integration(II)category learning are separate systems.So researchers argue that the difference between these two types of category learning is due to two separate learning systems,but some researchers argue that the difficulty of classification tasks results in the difference.Therefore,the paper takes patients with bipolar disorder as objects in order to explore the reasons for the difference between RB category learning and II category learning.According to the multiple-systems theory,RB and II category learning are two different learning systems,which rely on different neural mechanisms.The RB category learning depends on the explicit learning system supported the prefrontal cortex and medial temporal lobe,and the II category learning depends on the implicit learning system supported striatum.The studies of cognitive neuroscience in patients with bipolar disorder have shown that there are abnormalities in function and structure in frontal-limbic system loop.The studies of cognitive function also have shown that most of the patients have serious damage in explicit learning tasks.However,owning to the striatum which was influenced by whether patients are accompanied by psychotic symptoms and the implicit learning which was influenced by the degree of difficulties,the patients displayed different performance.Currently,few studies have directly compared the explicit learning and implicit learning of patients with bipolar disorder,and it is not clear about the degree of damage between them.Therefore,the study simultaneously investigates the performance of RB and II category learning in patients with bipolar disorder to explore that whether the II category learning is impaired,which could add to the evidence that the two types of category learning are separate,and further support multiple-systems theory.There are three researches in our study to explore the performance of RB and II category learning in patients with bipolar disorder.18 patients with bipolar disorder and 24 contol participants were asked to complete RB unidimension,RB dimensions and II category learning tasks in three days respectively.The performance of two typical category learning were investigated in patients with bipolar disorder in research 1(experiment 1),as the basis for researches.The results showed that learning in RB unidimension structure was better than that in II structure in patients with bipolar disorder.Because related dimensions and category structures are different,so we speculate that the reason for this difference may be the difference in the number of relevant dimensions,or the difference in category structures.There were two experiments to explore the reasons for the difference between RB category learning and II category learning in.patients with bipolar disorder.Experiment 2 examined the effect of the different related dimensions on the category learning under the same category structure.Experiment 3 examined the effect of different category structures on category learning under the same number of related dimensions.The results showed that,in RB category learning,unidimensional category learning was significantly better than the two dimensions category learning,which showed that the different number of related dimensions would cause differences in the category of learning in BD patients.Under two relevant dimensions category learning,RB category learning was significantly worse than II category learning.Even the balance of difficulty,II learning was still significantly better than RB learning.This suggested that the differences of category structures were also the cause of the differences between the two types of category learning,which supported the multiple-systems theory and revealed that patients with bipolar disorder are more impaired in RB category learning.The performance of three category learning tasks in patients bipolar disorder was compared to that of control participants in research 3(experiment 4).The results showed that the patients with bipolar disorder were significantly lower than those in the normal group in the three learning tasks,which indicated that patients was impaired both in explicit learning and implicit learning.Converging with two researches results could draw the following conclusions:(1)Compared to normal participants,patients with bipolar disorder are impaired in both types of category learning,not just in the explicit category learning;(2)After balancing the number of related dimensions and difficulty,RB learning was more impaired than the II learning in patients with bipolar disorder,which indicated that patients in bipolar disorder were more damaged in explicit category learning,supporting the multiple-systems theory;(3)Compared with RB unidimension category learning,RB two related dimensions learning was more damaged in patients with bipolar disorder,indicating that the number of related dimensions(difficulty)was also an important factor on category learning.