Gátló folyamatok az emlékezeti előhívásban = Inhibitory processes in memory retrieval

1)Laboratóriumi vizsgálatokat végeztünk egészséges, felnőtt vizsgálati személyek bevonásával az epizodikus előhívás során megfigyelhető gátlóhatások kognitív háttérmechanizmusainak elemzésére. Az emlékezeti irodalomban széleskörben alkalmazott gátlási paradigmák alkalmazásával megállapítottuk, hogy az intencionális emlékezeti gátlási folyamatok a végrehajtófunkiók működésétől függenek, kettős terhelési helyzetben károsodik a működésük, azonban ez a károsodás nem érinti az automatikus emlékezeti gátlási folyamatokat. Ugyancsak megállapítottuk, hogy az intencionális emlékezeti gátlás túlnyomórészben az autonoetikus tudatossággal jellemezhető emlékezeti folyamatokat érinti, a jelaktiváción alapuló noetikus folyamatok pedig csak automatikus gátlási hatásoknak vannak kitéve. 2)Agysérült betegek bevonásával megállapítottuk, hogy az intencionális emlékezeti és figyelmi gátlóhatás működése nagymértékben a jobb oldali frontális agyterületek működéséhez asszociálódik. A jobb frontális lézión átesett betegek jelentős károsodást mutattak irányított felejtési, Go/No-Go, Stroop feladatokban, míg az automatikus előhívási gátlás érintetlenül maradt náluk. 3) Mintegy 80 fős szkizofrén betegcsoport kognitív neuropszichiátriai vizsgálatát kezdtük meg. Első vizsgálataink során kimutattuk, hogy a szkizofréniában kimutatható végrehajtórendszer károsodás az intencionális emlékezeti gátlás károsodásával jár együtt , míg az automatikus emlékezeti gátlást nem érinti. | 1)We have runned experiments with healthy adult subjects to unfold the cognitive background of episodic retrieval inhibitory processes. Using widely applied experimental procedures we found that intentional retrieval inhibition depends on the executive system, as secondary memory load impaired intentionally elicited retrieval inhibition, however left the automatic inhibitory processes intact. We also found that intentional inhibition is only present in autonoetic episodic recall, while noetic recall processes are shaped by automatic inhibition. 2)In a series of experiments involving brain damaged patients and control subjects we found that intentional retrieval and attentional inhibition are associated to the intactness of the right frontal lobe. Patients produced impaired inhbition in directed forgetting, Go/No-go and Stroop tasks, however they showed normal automatic inhibition in the retrieval-induced forgetting task. 3)We have begun a long-term cognitive neuropsychiatric research program involving 80 schizophrenic patients Our first results show that the serious impairment of the executive system in schizophrenia is associated to the impairment of intentional retrieval ihhibition, but has no effect on the operation of the automatic inhibition of retrieval

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

How the size of the to-be-learned material influences the encoding and later retrieval of associative memories: A pupillometric assessment

Pupillometry have recently added valuable insights about the cognitive and possible neurobiological processes underlying episodic memory. Most of the studies, however, investigated recognition memory, which only partially relies on cue-driven recollection, the hallmark feature of episodic memory. Here we measured pupil size during a paired associate learning task, where participants encoded word-pairs, and after a short delay they took part in a cued recall. Importantly, we manipulated the size of the learning set: participants either learnt two, four or eight word-pairs in a row. As expected, increasing set size resulted in larger forgetting, assumingly as a consequence of weaker memory strength for the word-pairs. Our results show an important difference between pupil size changes observed during encoding and retrieval. During retrieval, the pupil instantly begun to dilate, as a sign of increased processing load accompanying the retrieval of the target memory. Importantly, large set size was also associated with larger pupil dilation during retrieval. This supports the notion that pupil dilation can be regarded as a marker of memory strength. In contrast, during encoding, pupil dilation decreased with increasing amount of encoded information, which might be due to the overuse of attentional resources. Furthermore, we also found that serial position during encoding modulated subsequent memory effects: for the first three serial positions, successful recall was predicted by larger pupil dilation during encoding, whereas such subsequent memory effect was absent for later serial positions. These results suggest that the amount of information independently modulates pupil dilation during encoding and retrieval, and support the assumption that pupillometric investigation of paired associate learning could be an informative way to investigate the cognitive and neurobiological processes of episodic memory

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

Végrehajtórendszer és emlékezeti előhívás: működés és patológia = Executive system and memory retrieval: function and pathology

Az emlékezeti gátlással foglalkozó vizsgálataink eredménye szerint az előhívási mintázatot a tanulás alatt létrehozott epizodikus reprezentáció mediálja, amely magában foglalja a tanulás alatt mozgósított konceptuális és más természetű tudás aktivációját/gátlását. Az epizodikus emlékezet hosszú távú konszolidációja során ez az aktivációs/gátlási mintázat, amely meghatározza az emlékezet tartalmának elérhetőségét stabilizálódik és ezáltal nehezen változtathatóvá válik. Eredményeink szerint az alvás lényeges szerepet játszik ebben a folyamatban. Vizsgálataink kimutatták, hogy szkizofréniával diagnosztizált személyek nem képesek szándékosan elfelejteni a korábban megtanult információkat, ezzel szemben egyértelmű gátlási hatást produkálnak szelektív gyakorlást követően. Ezek az eredmények arra utalnak, hogy a szikzofrénia spektrumban megjelenő végrehajtó rendszer deficit károsítja a betegek azon képességét, hogy intemcionálisan kiszorítsanak korábban elsajátított információkat. Saját szisztematikus neurokognitív vizsgálataink stabil állapotban lévő szkizofrén beteggel két klasztert azonosítottak a betegségen belül, melyek hátterében különböző patofiziológiai folyamatokra utaló eltéréseket találtunk. Obszesszív kompulzív betegek (OCD) prospektív emlékezeti (PM) funkcióit vizsgáló kísérleteink eredményei szerint a OCD betegek károsodott teljesítményt mutatnak a prospektív emléekezetet mozgító feladatokban, amelynek hátterében a PM ingerek túlmonitorozás állhat. | According to the result of ours studies concerning inhibitory memory control processes the recall patterns are mediated by an episodic memory of the study phase, and this will represent the patterns of activation/inhibition that predominated in conceptual and other knowledge networks during study. As the episodic memory is consolidated in long-term memory, the pattern of activation and inhibition, which determines the accessibility of the contents of the memory, stabilizes and becomes resistant to further change. Our findings suggest that sleep is important to this process of consolidation. Our results demonstrate that patients with schizophrenia are not able to intentionally inhibit previously studied items, but they produce a strong and reliable inhibitory effect in the selective practice procedure. In conclusion, the present experiments indicate that possible disrupted executive functions may considerably weaken the ability of patients with schizophrenic spectrum disorder to intentionally avoid recent memories. Our cross-sectional study on patients with schizophrenia revealed two subgroups in this sample that could be distinguished from each other on symptomatological, cognitive and neurological levels. We investigated prospective memory (PM) function in patients with obsessive-compulsive disorder (OCD). Our results suggest that OCD patients experience difficulties during PM tasks, and these difficulties originate from over-monitoring the stimuli for PM cues

Utak és kerülők emlékeinkhez : hozzáférhetőség vs. rendelkezésre állás irányított felejtés után

Az irányított felejtési kísérlet irodalma szerint képesek vagyunk szándékosan kiszorítani emlékeinket memóriánkból. Egyes magyarázatok szerint ezen emlékek gátlás alá kerültek, az előhívási folyamatok számára átmenetileg nem állnak rendelkezésre, újabb elképezések szerint azonban a gátlás nem a célemléket, hanem annak tanulási epizódját érinti, így ezek az emlékek rendelkezésre állnak, csak epizodikus hívóingerekkel el nem érhetőek. Két kísérletben e két megközelítést ütköztettük listás irányított felejtési paradigmát alkalmazva. A kísérletben használt 28 szó 14 meghatározott kategóriába tartozott, bár erről a tanulás során a kísérleti személyeket nem informáltuk. Első kísérletünkben három felidézési helyzet volt (1. szabad felidézés — implicit kategóriacímkével segített hívóingeres felidézés — 2. szabad felidézés). A felejts instrukciót kapott csoporteredménye mindkét szabad felidézésben gyengébb volt az emlékezési instrukciót kapottnál, de hívóingeres felidézésben nem volt különbség köztük. Az újabb (2. szabad felidézés) tesztben már csak a „felejts" csoport teljesítménye volt gyengébb a kategória-hívóingereshez képest, az „emlékezz" csoport esetében nem csökkent a teljesítmény. A második kísérletben két felidézési fázist (hívóingeres felidézés — 2. szabad felidézés) használtunk és reprodukáltuk az első kísérlet eredményeit, melyek összhangban vannak Racsmány és Conway 2006-os elméletével; a felejtési instrukció hatására létrejövő gátlás hozzáférési zavart okoz, de nem érinti az emlék reprezentációját. According to the literature on directed forgetting we are able to supress our unwanted memories. Anderson & Green's theory (2001) states that these items are under inhibition and we can't evoke them. However, according to a recent theory (Racsmány & Conway, 2006) items are available, but not accessible, and not the items themselves, but rather their encoding episode is under inhibition. We confronted the afore-named theories in two experiments. In the list method directed forgetting procedure (3 recalling phase) the „forget" group in free recall test recalled fewer items as the „remember" group. In cued recall the two groups' outputs were equal. Our findings correspond to Racsmány & Conway's (2006) Episodic Inhibition theory

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