Memory functions in obsessive-compulsive disorder (OCD)

Obsessive compulsive disorder (OCD) is a highly debilitating neuropsychiatric condition characterized by intrusive unwanted thoughts and/or repetitive, compulsive behavior or mental rituals. The exact nature of the neurocognitive deficit behind the clinical symptoms in OCD is still unclear. There is a growing amount of evidence for deficit of the executive system - shifting and inhibition components - in OCD, which is strongly related to fronto-basal loop dysfunctions (e.g. Chamberlain et al., 2005; Olley et al., 2007). In the first part of the talk we present the key neuropsychological models of OCD along with our main results regarding specific patterns of executive deficit in OCD. In addition to the executive impairment, many studies found impaired visual and spatial memory performance in this disorder (e.g. Moritz et al., 2003). In the second part of the talk we present two recent studies regarding visuo-spatial memory functions in a pool of Hungarian patients diagnosed with OCD. In Study 1 we applied the Rey Complex Figure Task and found that OCD patient performed significantly poorer in the copy and recall phase of the task in comparison to matched healthy control group. In Study 2 we developed a computer-based Visual Pattern Task to investigate the eye movement correlates of cognitive processes involved in visuo-spatial working memory functions. We will discuss the possible relationships between eye movement patterns, cognitive deficits and symptom severity. Keywords: executive functions, visuo-spatial memory, eye movement patterns, OC

Realizing delayed intentions: overactivated monitoring function in obsessive compulsive disorder (OCD)

Obsessive-compulsive disorder (OCD) is characterized by repetitive intrusive unwanted thoughts (obsessions) and repetitive behaviors (compulsions). It is generally thought that executive system is the main underlying cognitive factor of symptoms of OCD (Olley et al., 2007). Here we present two experiments aimed to investigate event based prospective memory (PM) functions in OCD. In the first experiment we adapted the experimental paradigm developed by Burgess et al. (2001), while in the second experiment we applied a modified dual-task paradigm, which required the altered execution and inhibition of responses to the same secondary task cues. According to our results the OCD group performed significantly slower on these tasks than the matched healthy control group. In the second experiment patients made significantly more false alarm type errors and there was a significant positive correlation between the number of false alarms and the PM subscale scores of the Prospective Retrospective Memory Questionnaire (PRMQ). These findings suggest that patients experience difficulties during event-based PM task and that these difficulties may originate from over-monitoring stimuli for possible PM cues and the disinhibition of activated out-of-date responses. Keywords: executive functions, prospective memory, OC

Goal attainment and memory suppression: Zeigernik reloaded

In two series of experiments we investigated the effect of goal fulfilment on accessibility of episodic memories. First, based on the pioneering work of Zeigarnik (1927) we developed a novel paradigm to test the role of goal attainment in episodic retrieval. In this task subjects have to complete word stems of category exemplars belonging to a given category, the completion of words were randomly interrupted in half of the categories. Following a delay, unexpected free recall, category-cued recall or recognition tasks were conducted. The results show that subjects tend to recall less items from the completed categories in the free recall task whereas such difference is absent in the category-cued recall and recognition tasks. Second, using a list method directed forgetting (DF) paradigm we found that replacing the forget instruction with a memory test, which informed participants that the learning event is finished, DF phenomena (i.e. lower recall rate of to be forgotten items compared to baseline items) can be simulated. We suggest that a forget instruction in a learning task is an effective goal completion cue. These results suggest that goal completion puts goal-relevant information in an available, but in a less accessible form for later retrieval

The effect of deep brain stimulation on cognitive performance in patients with Parkinson’s disease

Introduction: There is a growing number of studies focusing on the short, medium and long term effects of deep brain stimulation (DBS) on motor and cognitive functions in Parkinson’s disease (PD). Substantially smaller number of studies performed on the results of surgical treatment of drugresistant tremor in patients with secondary Parkinson syndrome (PS). In our study we aimed to assess the effect of DBS on main cognitive functions, depression and anxiety in PD and PS patients. Methods: Ten PD patients with bilateral subthalamic-DBS and ten PS patients with bilateral thalamic Vim-DBS were evaluated before and after the surgery. Surgical planning was based on frameless MRI to CT image fusion with custom-developed Vister-3D planning software. The procedure was performed with guidance of RM and MHT stereotactic systems. Intraoperatively 3 to 5-channel microelectrode recording has been applied with registration of LeadToools (Medtronic) or Neurospot (Neurostar) recording equipment. Model 3389 electrodes were implanted bilaterally in all cases and connected to Activa PC or Kinetra dual channel implantable pulse generators. Results/Conclusion: The electrode position has been controlled with postoperative CT to preoperative MRI and to tractography co-registration. The patients’ cognitive performance level and clinical profile was compared not just to their own baseline, but also to a proper clinical control group, un-operated patients with PD and PS. The neuropsychological screening was focused on short term verbal and visuo-spatial memory, attention and executive functions. The possible relationships between area of stimulation, symptom severity and cognitive functioning will be discussed

Differential vulnerability of different forms of skill learning in Parkinson’s disease

The striatal dopaminergic dysfunction in Parkinson’s disease (PD) has been associated with deficits in skill learning in a number of studies, but the results are inconclusive so far. Motor sequence learning (especially sequence-specific learning) is found to be deficient in the majority of studies using the Serial Reaction Time Task (SRTT; Siegert, Taylor, Weatherall, & Abernethy, 2006; Jackson et al., 1995; Ferraro, Balota and Connor, 1993; Pascual-Leone et al., 1993, Muslimovic et al., 2007; Gobel et al., 2013; but see Kwak et al., 2012), although results are contradictory when verbal response is required instead of button presses (Westwater et al. 1998; Smith, Siegert and McDowall 2001). While problems with motor sequences seem to be prevalent, PD patients show intact performance on Artificial Grammar Learning (AGL) tasks, suggesting that the sequencing problem may be response type- or task type-dependent (Smith, Siegert and McDowall 2001; Witt, Nühsman and Deuschl, 2002) Acquisition of nonsequential probabilistic associations also seems to be vulnerable as evidenced by impaired PD performance on a probabilistic category learning task (Knowlton, Mangels et al., 1996; Shohamy, Myers, Onlaor, & Gluck, 2004). Our aim was to explore the nature of the skill learning deficit by testing different types of skill learning (sequential versus nonsequential, motor versus verbal) in the same group of Parkinson’s patients. 14 patients with PD (mean age: 59.77 range: 45.5-74) were compared to age-matched typical adults using 1) a Serial Reaction Time Task (SRTT) testing the learning of motor sequences, 2) an Artificial Grammar Learning (AGL) task testing the extraction of regularities from auditory sequences and 3) a Weather prediction task (PCL-WP), testing probabilistic category learning in a non-sequential task. In motor sequence learning on the SRTT task, the two groups did not differ in accuracy; PD patients were generally slower, and analysis of z-transformed reaction times showed no evidence of sequence learning in PD. A deficit in artificial grammar learning was present only as a tendency in the PD group. The PD group showed evidence of learning on the PCL task, and their learning performance was not statistically different from that of the control group. These results partly support and also extend previous findings suggesting that motor skill learning is vulnerable in PD, while other forms of skill learning are less prone to impairment. Results are also in line with previous assumptions that mechanisms underlying artificial grammar learning and probabilistic categorization do not depend on the striatum (Reber & Squire, 1999; Skosnik et al., 2002)

Elfelejtjük az irreleváns információkat? - epizodikus emlékezeti előhívás vizsgálata kényszerbetegségben

Az obszesszív-kompulzív zavar (OCD, kényszerbetegség) egy súlyos neuropszichiátriai kórkép, melyet a nemkívánatos betörő gondolatok (obszessziók) és/vagy az ismétlődő kompulzív cselekvések, mentális rituálék (kompulziók) jellemeznek (Amerikai Pszichiátriai Társaság, 1994). A klinikai tünetek egyik lényeges kognitív háttérfaktoraként legtöbb szerző a végrehajtó rendszer diszfunkcióját emeli ki (Kuelz és mtsai., 2004; Abramovitch és mtsai., 2013), ami szorosan kapcsolódik a számos vizsgálat által kimutatott orbitofrontális és dorsalis anterior cinguláris deficitekhez OCD-ben (Milad és Rauch, 2012). Ugyanakkor Chamberlain és mtsai., (2005) szerint a végrehajtó rendszer nem minden aspektusa sérült OCD-ben. A klinikai tünetek és a fő kognitív deficitek - mint, a prepotens válasz gátlása, a szett váltás és a hatékony szervezési stratégia használat az emlékezeti próbákban – megmagyarázhatóak a kognitív és a viselkedési gátlás sérülésével. Előzetes kutatásokból tudjuk, hogy az emlékek előhívása a végrehajtó rendszer működését involválja, amely a cél emlékek aktiválása mellett csökkenti a versengő emléknyomok elérhetőségét. Ezt a hatást nevezzük előhívás kiváltotta felejtésnek (retrieval induced forgetting – RIF), amit leggyakrabban a szelektív gyakorlási paradigmával vizsgáltak. Az emlékezeti patológiák megértése szempontjából alapvető tudományos kérdés, hogy vajon a RIF hatás a versengés feloldásában szerepet játszó gátlási folyamatoknak vagy csupán az előhívott emlékek megerősödésének és interferenciájának tulajdonítható-e. Célunk, hogy egy klinikai vizsgálat keretében bizonyítékokat szerezzünk a végrehajtó kontroll folyamatok szerepéről a RIF hatás előidézésében. Mivel korábbi adatok szerint a RIF hatás összefügg a munkamemória kapacitással és a szorongás szintjével, ezért vizsgálatunkban ezeket a változókat is mértük. A vizsgálatban 25 OCD-vel diagnosztizált személy, illetve 25, kor és iskolázottság mentén illesztett, kontroll személy vett részt. Egy módosított szelektív gyakorlási paradigmát használtunk, mely alkalmas volt nem csak a találatok/hibázások, hanem az adott válaszok reakcióidejének a rögzítésére is. Eredményeink azt mutatják, hogy az emlékezeti előhívás gyakorlása mindkét csoportban a gyakorolt emlékek jobb felidézéséhez vezetett, azonban csak a kontroll csoportban vezetett RIF-hez, az OCD csoportban nem. Nem találtunk összefüggést a RIF hatás és az állapot, vonás szorongás mértéke között a (STAI) illetve a RIF hatás és a munka- (N-vissza feladatok), rövid távú memória kapacitás (Számterjedelem Előre feladat) között. Valószínűleg a RIF hatás hiánya az OCD-ben megfigyelhető konfliktus detektáló folyamatok zavarával magyarázható, melynek hátterében az anterior cinguláris és a prefrontális kéreg fokozott aktivitása valószínűsíthető. Kulcsszavak: emlékezet, előhívás kiváltotta felejtés, obszesszív kompulzív zavar, végrehajtó kontrol

Differential vulnerability of different forms of skill learning in Parkinson’s disease Different forms of skill learning in Parkinson’s disease

The striatal dopaminergic dysfunction in Parkinson’s disease (PD) has been associated with deficits in skill learning, but results are inconclusive so far. Motor sequence learning (especially sequence-specific learning) is found to be deficient in the majority of studies using the SRT task (Jackson, Jackson, Harrison, Henderson, & Kennard, 1995; Siegert, Taylor, Weatherall, & Abernethy, 2006). While problems with motor sequences seem to be prevalent, PD patients show intact performance on AGL tasks, suggesting that the sequencing problem may be response- or taskdependent (Reber & Squire, 1999). Acquisition of nonsequential probabilistic associations also seems to be vulnerable as evidenced by impaired probabilistic category learning performance in PD (Knowlton, Mangels, & Squire, 1996; Shohamy, Myers, Onlaor, & Gluck, 2004). Our aim was to explore the nature of the skill learning deficit by testing different types of skill learning (sequential versus nonsequential, motor versus verbal) in the same group of Parkinson’s patients. 34 patients with PD (mean age: 62.59.77 years, SD: 7.67) were compared to age-matched typical adults using 1) a Serial Reaction Time Task (SRT) testing the learning of motor sequences, 2) an Artificial Grammar Learning (AGL) task testing the extraction of regularities from auditory sequences and 3) a Weather prediction task (PCL-WP), testing probabilistic category learning in a non-sequential task. In motor sequence learning (SRT task), the two groups did not differ in accuracy; PD patients were generally slower, and analysis of z-transformed reaction times also revealed deficient motor sequence learning in PD compared to the control group. The PD group showed no evidence of sequence learning. The PD group showed the same amount of learning on the PCL task as controls, and we observed higher rates of learning on the AGL task in PD patients than in controls. These results support and also extend previous findings suggesting that motor skill learning is vulnerable in PD, while other forms of skill learning are less prone to impairment. Results are also in line with previous assumptions that mechanisms underlying artificial grammar learning and probabilistic categorization do not depend on the striatum (Reber & Squire, 1999)