Implicit and Explicit Memory in Depression/ Dysphoria: an Analysis of the Contribution of Perceptual and Conceptual Processes

<p>Earlier studies have shown impaired explicit test and normal implicit test performance in participants classified as depressed. A number of different models have been put forward to explain this 'typical' test dissociation including the memory systems, processing, and activation - elaboration models. Blaxton (1989, 1992) has pointed out that to date most test designs have confounded the memory systems and processing models. The aim of this series of experiments was to systematically compare the effects of depression on the processing and memory systems models and in so doing provide a more precise explanation for the effects of depression on human memory. Across Experiments 1 - 4 the performance of participants with depression or dysphoria were examined on implicit and explicit memory tests which were designed to tap either predominantly perceptual or conceptual processes. In Experiment 1 the conceptual tests of category association (implicit) and semantic cued recall (explicit) were compared with the perceptual tests of word fragment completion (implicit) and graphemic cued recall (explicit). In Experiment 2 the perceptual tests of perceptual identification (implicit) and the 'mixed' test of anagram solution (implicit) were compared with the conceptual free recall test (explicit). Both experiments used dysphoric university students and found no effects of dysphoria in comparison to normal controls matched for age, sex and education levels. Experiment 3 compared the conceptual category association (implicit) and free recall (explicit) tests with the perceptual word fragment completion test (implicit) using participants diagnosed with major depression disorder. This revealed significant impairments in both the conceptual tests while the perceptual test was intact. Experiment 4 compared the implicit word association test with the explicit word association test using dysphoric university students. Experiment 4 found that dysphoric participants were impaired in performing the explicit test while the implicit test remained intact. These findings suggest that dysphoria has no effect on implicit tests, but can effect conceptual explicit test measures. Clinical depression effects both conceptual implicit and conceptual explicit test measures. While these results support aspects of both the memory systems and processing models these findings may be best accommodated by a model which combines these models. The revised memory systems model is discussed as one means of achieving this.</p>

Implicit and Explicit Memory in Depression/ Dysphoria: an Analysis of the Contribution of Perceptual and Conceptual Processes

<p>Earlier studies have shown impaired explicit test and normal implicit test performance in participants classified as depressed. A number of different models have been put forward to explain this 'typical' test dissociation including the memory systems, processing, and activation - elaboration models. Blaxton (1989, 1992) has pointed out that to date most test designs have confounded the memory systems and processing models. The aim of this series of experiments was to systematically compare the effects of depression on the processing and memory systems models and in so doing provide a more precise explanation for the effects of depression on human memory. Across Experiments 1 - 4 the performance of participants with depression or dysphoria were examined on implicit and explicit memory tests which were designed to tap either predominantly perceptual or conceptual processes. In Experiment 1 the conceptual tests of category association (implicit) and semantic cued recall (explicit) were compared with the perceptual tests of word fragment completion (implicit) and graphemic cued recall (explicit). In Experiment 2 the perceptual tests of perceptual identification (implicit) and the 'mixed' test of anagram solution (implicit) were compared with the conceptual free recall test (explicit). Both experiments used dysphoric university students and found no effects of dysphoria in comparison to normal controls matched for age, sex and education levels. Experiment 3 compared the conceptual category association (implicit) and free recall (explicit) tests with the perceptual word fragment completion test (implicit) using participants diagnosed with major depression disorder. This revealed significant impairments in both the conceptual tests while the perceptual test was intact. Experiment 4 compared the implicit word association test with the explicit word association test using dysphoric university students. Experiment 4 found that dysphoric participants were impaired in performing the explicit test while the implicit test remained intact. These findings suggest that dysphoria has no effect on implicit tests, but can effect conceptual explicit test measures. Clinical depression effects both conceptual implicit and conceptual explicit test measures. While these results support aspects of both the memory systems and processing models these findings may be best accommodated by a model which combines these models. The revised memory systems model is discussed as one means of achieving this.</p>

Implicit and Explicit Memory in Youths with High-Functioning Autism Spectrum Disorder: A Case-Control Study

Individuals with autism spectrum disorder (ASD) usually manifest heterogeneous impairments in their higher cognitive functions, including their implicit memory (IM) and explicit memory (EM). However, the findings on IM and EM in youths with ASD remain debated. The aim of this study was to clarify such conflicting results by examining IM and EM using two comparable versions of the Serial Reaction Time Task (SRTT) in the same group of children and adolescents with ASD. Twenty-five youths with high-functioning ASD and 29 age-matched and IQ-matched typically developing youths undertook both tasks. The ability to implicitly learn the temporal sequence of events across the blocks in the SRTT was intact in the youths with ASD. When they were tested for EM, the participants with ASD did not experience a significant reduction in their reaction times during the blocks with the previously learned sequence, suggesting an impairment in EM. Moreover, the participants with ASD were less accurate and made more omissions than the controls in the EM task. The implications of these findings for the establishment of tailored educational programs for children with high-functioning ASD are discussed.

Aging II

Chapter 8 focuses on empirical studies of age-related differences in memory performance. In accordance with the concepts of environmental support and self-initiated activities it is shown that age decrements are greater in cued recall than in recognition, also that cued recall is more resource-demanding than recognition. A further study found that age-related deficits were reduced by the use of semantically related materials but that older adults showed greater dual-task costs, especially at the time of retrieval. Age-related impairments were reduced by the use of pictorial materials as opposed to words; and reinstatement of the encoding context at retrieval was particularly helpful to older adults. A study carried out in California showed how individual differences in verbal intelligence and in daily activity levels modified the pattern of findings. The point that older adults have difficulty retrieving highly specific information is discussed and illustrated. Experiments are described that investigate memory for the source of learned information, and for age differences in prospective memory; younger adults outperformed their older counterparts in both situations. Finally, some interesting patterns of age differences in performance of implicit and explicit memory tasks are described and discussed.

Local Processing Bias Impacts Implicit and Explicit Memory in Autism

Autism spectrum disorder (ASD) is characterized by atypical perception, including processing that is biased toward local details rather than global configurations. This bias may impact on memory. The present study examined the effect of this perception on both implicit (Experiment 1) and explicit (Experiment 2) memory in conditions that promote either local or global processing. The first experiment consisted of an object identification priming task using two distinct encoding conditions: one favoring local processing (Local condition) and the other favoring global processing (Global condition) of drawings. The second experiment focused on episodic (explicit) memory with two different cartoon recognition tasks that favored either local (i.e., processing specific details) or a global processing (i.e., processing each cartoon as a whole). In addition, all the participants underwent a general clinical cognitive assessment aimed at documenting their cognitive profile and enabling correlational analyses with experimental memory tasks. Seventeen participants with ASD and 17 typically developing (TD) controls aged from 10 to 16 years participated to the first experiment and 13 ASD matched with 13 TD participants were included for the second experiment. Experiment 1 confirmed the preservation of priming effects in ASD but, unlike the Comparison group, the ASD group did not increase his performance as controls after a globally oriented processing. Experiment 2 revealed that local processing led to difficulties in discriminating lures from targets in a recognition task when both lures and targets shared common details. The correlation analysis revealed that these difficulties were associated with processing speed and inhibition. These preliminary results suggest that natural perceptual processes oriented toward local information in ASD may impact upon their implicit memory by preventing globally oriented processing in time-limited conditions and induce confusion between explicit memories that share common details.

Sex Does Not Sell: Effects of Sexual Advertising Parameters on Women Viewers’ Implicit and Explicit Recall of Ads and Brands

This study investigated implicit and explicit memory effects of sexual and non-sexual advertisements embedded in either a sexual or non-sexual program among women viewers. We predicted that sexual appeals would facilitate implicit memory for the brand, and we explored whether program-type (sexual or non-sexual) and its associated congruity would impact or moderate recall of the surrounding advertisement among a small sample (n = 52) of exclusively women advertisement viewers. Sexual (versus non-sexual) advertising led to significantly worse implicit memory for the brand logo but better explicit recall for the advertisement scene itself. There was no effect of sexual appeals on explicit brand name recall, and no significant effect on advertisement recall of the program type. There was a significant interaction effect for program type and advertisement type for explicit recall of the advertisement scene, in which program-type moderated sexual advertisement recall. These results suggest that sexual advertising may increase memory for the advertisement at the expense of recalling the brand advertised. Limitations and implications of this study are discussed.

Functional dissociation of hippocampal subregions corresponding to memory types and stages

Background The hippocampus reportedly plays a crucial role in memory. However, examining individual human hippocampal-subfield function remains challenging because of their small sizes and convoluted structures. Here, we identified hippocampal subregions involved in memory types (implicit and explicit memory) and stages (encoding and retrieval). Methods We modified the serial reaction time task to examine four memory types, i.e. implicit encoding, explicit encoding, implicit retrieval, and explicit retrieval. During this task, 7-T functional magnetic resonance imaging was used to compare brain activity evoked by these memory types. Results We found hippocampal activation according to all memory types and stages and identified that the hippocampus subserves both implicit and explicit memory processing. Moreover, we confirmed that cornu ammonis (CA) regions 1–3 were implicated in both memory encoding and retrieval, whereas the subiculum was implicated only in memory retrieval. We also found that CA 1–3 was activated more for explicit than implicit memory. Conclusions These results elucidate human hippocampal-subfield functioning underlying memory and may support future investigations into hippocampal-subfield functioning in health and neurodegenerative disease.

Implicit and explicit systems differently predict possible dangers

One strategy to address new potential dangers is to generate defensive responses to stimuli that remind learned threats, a phenomenon called fear generalization. During a threatening experience, the brain encodes implicit and explicit memory traces. Nevertheless, there is a lack of studies comparing implicit and explicit response patterns to novel stimuli. Here, by adopting a discriminative threat conditioning paradigm and a two-alternative forced-choice recognition task, we found that the implicit reactions were selectively elicited by the learned threat and not by a novel similar but perceptually discriminable stimulus. Conversely, subjects explicitly misidentified the same novel stimulus as the learned threat. This generalization response was not due to stress-related interference with learning, but related to the embedded threatening value. Therefore, we suggest a dissociation between implicit and explicit threat recognition profiles and propose that the generalization of explicit responses stems from a flexible cognitive mechanism dedicated to the prediction of danger.

Implicit perceptual memory can increase or decrease with ageing

ABSTRACTA decline in declarative or explicit memory has been extensively characterized in cognitive ageing and is a hallmark of cognitive impairments. However, whether and how implicit perceptual memory varies with ageing or cognitive impairment is unclear. Here, we compared implicit perceptual memory and explicit memory measures in three groups of subjects: (1) 59 healthy young volunteers (20-30 years); (2) 238 healthy old volunteers (50-90 years) and (3) 21 patients with mild cognitive impairment MCI (50-90 years). To measure explicit memory, subjects were tested on standard recognition and recall tasks. To measure implicit perceptual memory, we used a classic perceptual priming paradigm. Subjects had to report the shape of a visual search pop-out target. Implicit priming was measured as the speedup in response time for targets with the same vs different color/position on consecutive trials.Our main findings are as follows: (1) Explicit memory was weaker in old compared to young subjects, and in MCI compared to age-matched controls; (2) Surprisingly, implicit perceptual memory did not always decline with age: color priming was smaller in older subjects but position priming was larger; (3) Position priming was less frequent in the MCI group compared to age-matched controls; (4) Implicit and explicit memory measures were uncorrelated in all three groups. Thus, implicit memory can increase or decrease with age or cognitive impairment, but this decline does not covary with explicit memory. We propose that incorporating explicit and implicit measures can yield a richer characterization of memory.