Investigating the functional interaction between semantic and episodic memory: convergent behavioral and electrophysiological evidence for the role of familiarity

Throughout our lives we acquire general knowledge about the world (semantic memory) while also retaining memories of specific events (episodic memory). Although these two forms of memory have been dissociated on the basis of neuropsychological data, it is clear that they typically function together during normal cognition. The goal of the present study was to investigate this interaction. One influence of semantic memory on episodic retrieval is 'Levels Of Processing'; recognition is enhanced when stimuli are processed in a semantically meaningful way. Studies examining this semantic processing advantage have largely concluded that semantic memory augments episodic retrieval primarily by enhancing recollection. The present study provides strong evidence for an alternative relationship between semantic and episodic memory. We employed a manipulation of the semantic coherence of to-be-remembered information (semantically related vs. unrelated word pairs) during an associative recognition memory test. Results revealed that associative recognition is significantly enhanced for semantically coherent material, and behavioral estimates (using the process dissociation procedure) demonstrated concomitant changes in the contribution of familiarity to retrieval. Neuroimaging data (event-related potentials recorded at test) also revealed a significant increase in familiarity based retrieval. The electrophysiological correlate of familiarity (the mid-frontal ERP old/new effect) was larger for semantically related compared to unrelated word pairs, but no difference was present in the electrophysiological correlate of recollection (the left parietal old/new effect). We conclude that semantic memory and episodic memory do indeed interact in normal functioning, and not only by modulating recollection, but also by enhancing familiarity.     

Oscillatory correlates of the primacy effect in episodic memory

Both intracranial and scalp EEG studies have demonstrated that oscillatory activity, especially in the gamma band (28 to 100 Hz), can differentiate successful and unsuccessful episodic encoding [Sederberg, P.B., Kahana, M.J., Howard, M.W., Donner, E.J., Madsen, J.R., 2003. Theta and gamma oscillations during encoding predict subsequent recall. Journal of Neuroscience, 23(34), 10809-10814; Fell, J., Klaver, P., Lehnertz, K., Grunwald, T., Schaller, C., Elger, C.E., Fernandez, G., 2001. Human memory formation is accompanied by rhinal-hippocampal coupling and decoupling. Nature Neuroscience, 4 (12), 1259-1264; Gruber, T., Tsivilis, D., Montaldi, D., and Müller, M. (2004). Induced gamma band responses: An early marker of memory encoding and retrieval. Neuroreport, 15, 1837-1841; Summerfield, C., Mangels, J.A., in press. Dissociable neural mechanisms for encoding predictable and unpredictable events. Journal of Cognitive Neuroscience]. Although the probability of recalling an item varies as a function of where it appeared in the list, the relation between the oscillatory dynamics of successful encoding and serial position remains unexplored. We recorded scalp EEG as participants studied lists of common nouns in a delayed free-recall task. Because early list items were recalled better than items from later serial positions (the primacy effect), we analyzed encoding-related changes in 2 to 100 Hz oscillatory power as a function of serial position. Increases in gamma power in posterior regions predicted successful encoding at early serial positions; widespread low-frequency (4-14 Hz) power decreases predicted successful memory formation for later serial positions. These results suggest that items in early serial positions receive an encoding boost due to focused encoding without having to divide resources among numerous list items. Later in the list, as memory load increases, encoding is divided between multiple items.     

Dissociating recollection from familiarity: electrophysiological evidence that familiarity for faces is associated with a posterior old/new effect

In recognition memory research, a tension exists between dual-process and single-process models of episodic retrieval. Dual-process models propose that 'familiarity' assessment and the 'recollection' of contextual information are independent processes, while single-process models claim that one common process supports retrieval. Event-related potentials (ERPs) have been used to show dissociations between the mid frontal and the left parietal ERP old/new effects, which have been associated with familiarity and recollection, respectively. While much ERP evidence favours dual-process theory, Yovel and Paller [Yovel, G., Paller, K.A., 2004. The neural basis of the butcher-on-the-bus phenomenon: when a face seems familiar but is not remembered. NeuroImage 21, 789-800] used faces as retrieval cues to demonstrate that posterior old/new effects index both familiarity and recollection, a finding consistent with single-process models. Here we present evidence supporting Yovel and Paller's claim that a posterior old/new effect indexes familiarity for faces, along with a novel finding that recollection is associated with an anterior old/new effect. Importantly, and in contrast to Yovel and Paller, the old/new effects associated with familiarity and recollection were topographically dissociable, consistent with a dual-process view of recognition memory. The neural correlates of familiarity and recollection identified here for faces appear to be different from those typically observed, suggesting that the ERP old/new effects associated with episodic recognition are not the same under all circumstances.     

Examining ERP correlates of recognition memory: evidence of accurate source recognition without recollection

Recollection is typically associated with high recognition confidence and accurate source memory. However, subjects sometimes make accurate source memory judgments even for items that are not confidently recognized, and it is not known whether these responses are based on recollection or some other memory process. In the current study, we measured event related potentials (ERPs) while subjects made item and source memory confidence judgments in order to determine whether recollection supported accurate source recognition responses for items that were not confidently recognized. In line with previous studies, we found that recognition memory was associated with two ERP effects: an early on-setting FN400 effect, and a later parietal old-new effect [late positive component (LPC)], which have been associated with familiarity and recollection, respectively. The FN400 increased gradually with item recognition confidence, whereas the LPC was only observed for highly confident recognition responses. The LPC was also related to source accuracy, but only for items that had received a high confidence item recognition response; accurate source judgments to items that were less confidently recognized did not exhibit the typical ERP correlate of recollection or familiarity, but rather showed a late, broadly distributed negative ERP difference. The results indicate that accurate source judgments of episodic context can occur even when recollection fails.     

The effect of word concreteness on recognition memory

Concrete words that are readily imagined are better remembered than abstract words. Theoretical explanations for this effect either claim a dual coding of concrete words in the form of both a verbal and a sensory code (dual-coding theory), or a more accessible semantic network for concrete words than for abstract words (context-availability theory). However, the neural mechanisms of improved memory for concrete versus abstract words are poorly understood. Here, we investigated the processing of concrete and abstract words during encoding and retrieval in a recognition memory task using event-related functional magnetic resonance imaging (fMRI). As predicted, memory performance was significantly better for concrete words than for abstract words. Abstract words elicited stronger activations of the left inferior frontal cortex both during encoding and recognition than did concrete words. Stronger activation of this area was also associated with successful encoding for both abstract and concrete words. Concrete words elicited stronger activations bilaterally in the posterior inferior parietal lobe during recognition. The left parietal activation was associated with correct identification of old stimuli. The anterior precuneus, left cerebellar hemisphere and the posterior and anterior cingulate cortex showed activations both for successful recognition of concrete words and for online processing of concrete words during encoding. Additionally, we observed a correlation across subjects between brain activity in the left anterior fusiform gyrus and hippocampus during recognition of learned words and the strength of the concreteness effect. These findings support the idea of specific brain processes for concrete words, which are reactivated during successful recognition.     

Context-dependent interpretation of words: evidence for interactive neural processes

The meaning of a word usually depends on the context in which it occurs. This study investigated the neural mechanisms involved in computing word meanings that change as a function of syntactic context. Current semantic processing theories suggest that word meanings are retrieved from diverse cortical regions storing sensory-motor and other types of semantic information and are further integrated with context in left inferior frontal gyrus (LIFG). Our fMRI data indicate that brain activity in an area sensitive to motion and action semantics--the posterior middle temporal gyrus (PMTG)--is modulated by a word's syntactic context. Ambiguous words such as bowl were presented in minimal disambiguating contexts indicating object (the bowl) or action (to bowl) meanings and were compared to low-ambiguity controls. Ambiguous words elicited more activity than low-ambiguity controls in LIFG and various meaning-related areas such as PMTG. Critically, ambiguous words also elicited more activity in to--contexts than the--contexts in PMTG and LIFG, suggesting that contextual integration strengthened the action meaning in both areas. The pattern of results suggests that the activation of lexical information in PMTG was sensitive to contextual disambiguating information and that processing context-dependent meanings may involve interactions between frontal and posterior areas.     

Isolating the retrieval of imagined pictures during episodic memory: activation of the left precuneus and left prefrontal cortex

The posterior medial parietal cortex and the left prefrontal cortex have both been implicated in the recollection of past episodes. In order to clarify their functional significance, we performed this functional magnetic resonance imaging study, which employed event-related source memory and item recognition retrieval of words paired with corresponding imagined or viewed pictures. Our results suggest that episodic source memory is related to a functional network including the posterior precuneus and the left lateral prefrontal cortex. This network is activated during explicit retrieval of imagined pictures and results from the retrieval of item-context associations. This suggests that previously imagined pictures provide a context with which encoded words can be more strongly associated.     

Effects of semantic relatedness on age-related associative memory deficits: the role of theta oscillations

Growing evidence suggests that age-related deficits in associative memory are alleviated when the to-be-associated items are semantically related. Here we investigate whether this beneficial effect of semantic relatedness is paralleled by spatio-temporal changes in cortical EEG dynamics during incidental encoding. Young and older adults were presented with faces at a particular spatial location preceded by a biographical cue that was either semantically related or unrelated. As expected, automatic encoding of face-location associations benefited from semantic relatedness in the two groups of age. This effect correlated with increased power of theta oscillations over medial and anterior lateral regions of the prefrontal cortex (PFC) and lateral regions of the posterior parietal cortex (PPC) in both groups. But better-performing elders also showed increased brain-behavior correlation in the theta band over the right inferior frontal gyrus (IFG) as compared to young adults. Semantic relatedness was, however, insufficient to fully eliminate age-related differences in associative memory. In line with this finding, poorer-performing elders relative to young adults showed significant reductions of theta power in the left IFG that were further predictive of behavioral impairment in the recognition task. All together, these results suggest that older adults benefit less than young adults from executive processes during encoding mainly due to neural inefficiency over regions of the left ventrolateral prefrontal cortex (VLPFC). But this associative deficit may be partially compensated for by engaging preexistent semantic knowledge, which likely leads to an efficient recruitment of attentional and integration processes supported by the left PPC and left anterior PFC respectively, together with neural compensatory mechanisms governed by the right VLPFC.     

Response of the renal K+-conserving mechanism to kaliuretic stimuli: evidence for a direct kaliuretic effect by furosemide

Isolated perfused kidneys from rats given a K+-free diet for 3 days demonstrate striking renal K+ conservation by a mechanism that is independent of perfusate and renal tissue K+, aldosterone, urine pH, urine flow, and sodium and anion excretion. To examine the effect of several kaliuretic stimuli on this intrinsic renal K+-conserving mechanism, kidneys from K+-depleted rats perfused with 3.5 mmol/L K+ were subjected to an experimental maneuver after 45 minutes of perfusion under normal conditions. Fractional potassium excretion (FEK) remained stable in time controls during a subsequent 45 minutes of perfusion. Acidification of the perfusate to pH 6.96 by addition of HCI had no significant effect on FEK. Alkalinization to pH 7.7 by either addition of NaHCO3 or a reduction in PCO2 resulted in significant kaliuresis (FEK 26% vs. 15%), which appeared to be a direct result of systemic alkalinization. Addition of Na2SO4 to the perfusate also produced significant kaliuresis (FEK 29%), which could not be dissociated from the magnitude of the natriuresis. Although both alkalosis and sulfate increased K+ excretion by depleted kidneys, FEK was much lower than with kidneys from normal rats perfused at pH 7.4 (FEK 51%). Thus the intrinsic renal K+-conserving mechanism dramatically diminishes the kidneys' kaliuretic potency and probably accounts for the blunted kaliuretic effect of these stimuli during K+ depletion in vivo. An increase in sodium excretion and urine flow rate achieved by lowering the perfusate albumin concentration, increasing the perfusate pressure, or adding the diuretics hydrochlorothiazide and furosemide resulted in significant kaliuresis.(ABSTRACT TRUNCATED AT 250 WORDS)     

A randomized control trial: the effect of guided imagery with tape and perceived happy memory on chronic tension type headache

Scand J Caring Sci; 2012; 26; 254–261 A randomized control trial: the effect of guided imagery with tape and perceived happy memory on chronic tension type headache Purpose: To determine the effects of guided imagery techniques with tape and perceived happy memory on people with chronic tension‐type headache (CTTH). Methods: Sixty people with CTTH completed the demographic questionnaire and headache diary 1 week before the treatment, that is, for 3 weeks during the treatment and 1 week immediately after that. The people were randomly assigned into one of three different treatment groups: a Guided imagery (GI) with tape group (n = 20), a GI with perceived happy memory group (n = 20) and a control group (n = 20). In addition to individualized headache therapy, subjects listened to a guided imagery audiocassette tape or imagined the happiest personal memory three times per week for 3 weeks. It should be noted that 20 control subjects received individualized therapy without guided imagery. Results: The guided imagery groups both tape and perceived happy memory had significantly more improvement than the controls in three of the outcome measures; headache intensity, headache frequency and headache duration. There were no other significant differences between the guided imagery groups (tape and perceived happy memory) at any time point. Conclusions: Guided imagery is an effective, available and affordable nonpharmacological therapy either with tape or with perceived happy memory for the management of the CTTH.     

Probing the transformation of discontinuous associations into episodic memory: an event-related fMRI study

Using event-related functional magnetic resonance imaging, we identified brain regions involved in storing associations of events discontinuous in time into long-term memory. Participants were scanned while memorizing item-triplets including simultaneous and discontinuous associations. Subsequent memory tests showed that participants remembered both types of associations equally well. First, by constructing the contrast between the subsequent memory effects for discontinuous associations and simultaneous associations, we identified the left posterior parahippocampal region, dorsolateral prefrontal cortex, the basal ganglia, posterior midline structures, and the middle temporal gyrus as being specifically involved in transforming discontinuous associations into episodic memory. Second, we replicated that the prefrontal cortex and the medial temporal lobe (MTL) especially the hippocampus are involved in associative memory formation in general. Our findings provide evidence for distinct neural operation(s) that supports the binding and storing discontinuous associations in memory. We suggest that top-down signals from the prefrontal cortex and MTL may trigger reactivation of internal representation in posterior midline structures of the first event, thus allowing it to be associated with the second event. The dorsolateral prefrontal cortex together with basal ganglia may support this encoding operation by executive and binding processes within working memory, and the posterior parahippocampal region may play a role in binding and memory formation.     

Human cortical EEG rhythms during long-term episodic memory task. A high-resolution EEG study of the HERA model

Many recent neuroimaging studies of episodic memory have indicated an asymmetry in prefrontal involvement, with the left prefrontal cortex more involved than the right in encoding, the right more than the left in retrieval (hemispheric encoding and retrieval asymmetry, or HERA model). In this electroencephalographic (EEG) high-resolution study, we studied brain rhythmicity during a visual episodic memory (recognition) task. The theta (4-6 Hz), alpha (6-12 Hz) and gamma (28-48 Hz) oscillations were investigated during a visuospatial long-term episodic memory task including an encoding (ENC) and retrieval (RET) phases. During the ENC phase, 25 figures representing interiors of buildings ("indoor") were randomly intermingled with 25 figures representing landscapes ("landscapes"). Subject's response was given at left ("indoor") or right ("landscapes") mouse button. During the RET phase (1 h later), 25 figures representing previously presented "indoor" pictures ("tests") were randomly intermingled with 25 figures representing novel "indoor" ("distractors"). Again, a mouse response was required. Theta and alpha EEG results showed no change of frontal rhythmicity. In contrast, the HERA prediction of asymmetry was fitted only by EEG gamma responses, but only in the posterior parietal areas. The ENC phase was associated with gamma EEG oscillations over left parietal cortex. Afterward, the RET phase was associated with gamma EEG oscillations predominantly over right parietal cortex. The predicted HERA asymmetry was thus observed in an unexpected location. This discrepancy may be due to the differential sensitivity of neuroimaging methods to selected components of cognitive processing. The strict relation between gamma response and perception suggests that retrieval processes of long-term memory deeply impinged upon sensory representation of the stored material.     

Lateralization of the parietal old/new effect: an event-related fMRI study comparing recognition memory for words and faces

Although the parietal cortex is not conventionally thought of as a major component of the neural systems that mediate declarative memory, many fMRI studies of recognition memory have found that correctly identified old items produce greater activation than correctly rejected new items throughout parietal cortex. This effect is usually heavily lateralized to the left. However, the vast majority of previous studies have used verbal materials. Does the left-lateralization of this effect result from the left hemisphere's role in language or does it suggest the possibility of a specialized role for the left hemisphere in recognition memory that applies across stimulus domains? To address this question, we directly compared recognition memory for words and faces in two event-related fMRI experiments with a total of 38 subjects. In the second experiment, we included a manipulation of recognition difficulty. Despite extensive material-specific lateralization in terms of the brain's overall response to stimuli revealed by a direct comparison of words and faces, the parietal old/new effect did not exhibit material-specific lateralization. Rather, the lateralization of the effect depended on the region of parietal cortex in question. In lateral parietal cortex, the effect was left-lateralized. In medial parietal cortex, the effect was bilateral. These findings indicate that the left-lateralization of the parietal old/new effect is unrelated to the left hemisphere's role in language and raises the possibility of a specialized role for the left hemisphere in recognition memory.     

Electrophysiological evidence for presynaptic actions of phencyclidine on noradrenergic transmission in rat cerebellum

The actions of the psychotomimetic drug phencyclidine (PCP) were studied using Purkinje neurons in the cerebellum of urethane-anesthetized rats. PCP, applied by micropressure ejection through multibarreled micropipettes, depressed the spontaneous activity of these neurons as recorded by extracellular electrophysiological techniques. This depressant effect was blocked by neuroleptic drugs and lithium, both of which also block the depressant effects of norepinephrine, but not those of gamma-aminobutyric acid. PCP-elicited depressions could not be obtained in rats in which the cerebellar noradrenergic terminals had been lesioned selectively by pretreatment with the neurotoxin 6-hydroxydopamine. However, PCP was still an effective depressant in animals after destruction of non-noradrenergic intrinsic excitatory and inhibitory interneurons which synapse on the Purkinje cell by neonatal X-irradiation. Further treatment of the X-irradiated animal with 6-hydroxy-dopamine resulted in Purkinje neurons which were not responsive to PCP. Administration of magnesium ions, which reduces the release of neurotransmitters from afferent terminals, also blocked the depressant effects of PCP. The results of this study suggest that PCP acts in the cerebellum by a presynaptic mechanism involving the release of norepinephrine from intact, functioning noradrenergic terminals.     

The role of the prefrontal cortex in recognition memory and memory for source: an fMRI study.

We employed fMRI to index neural activity in prefrontal cortex during tests of recognition and source memory. At study, subjects were presented with words displayed either to the left or right of fixation, and, depending on the side, performed one of two orienting tasks. The test phase consisted of a sequence of three 10-word blocks, displayed in central vision. For one block, subjects performed recognition judgements on a mixture of two old and eight new words (low density recognition). For another block, recognition judgements were performed on a mixture of eight old and two new words (high density recognition). In the remaining block, also consisting of eight old and two new items, the requirement was to judge whether each word had been presented at study on the left or the right. Relative to the low density condition, high density recognition was associated with increased activity in right and, to a lesser extent, left, anterior prefrontal cortex (BA 10), replicating the findings of two previous PET studies. Right anterior prefrontal activity did not show any further increase during the source task. Instead, greater activity was found, relative to high density recognition, in left BA 10, left inferior frontal gyrus (BA 45/47), and bilateral opercular cortices (BA 45/47). The findings are inconsistent with the proposal that activation of right anterior prefrontal cortex during memory retrieval reflects "postretrieval" processing demands, such demands being considerably greater for judgments of source than recognition. The findings provide further evidence that the left prefrontal cortex plays a role in episodic memory retrieval when the task explicitly requires recovery of contextual as well as item information.     

The effect of headache pain on attention (encoding) and memory (recognition)

Memory is a key cognitive variable in pain management. This study examined the effect of headaches on participants' encoding of words (attention) and later memory for words. The dependent measures were response time during encoding and recognition memory; headache pain was the independent measure. Eighty participants were randomized to one of four groups: two groups had the same condition (headache pain or no headache pain) for both the encoding and memory tasks and two groups had mixed conditions (i.e. pain during encoding/no pain during recognition; no pain during encoding/pain during recognition). Participants with pain during encoding judged words significantly slower (177.53ms) than participants without pain during encoding. Participants with pain during the memory task recognized significantly fewer words (5.4%) than participants without pain during the memory task, regardless of pain condition during encoding. Results from this and other pain and memory studies conducted in this laboratory suggest that pain, as it adversely affects memory, may operate at a threshold level rather than on a dose-response continuum.     

Electrophysiological evidence of intuition: part 1. The surprising role of the heart

OBJECTIVES: This study aims to contribute to a scientific understanding of intuition, a process by which information normally outside the range of conscious awareness is perceived by the psychophysiological systems. The first objective, presented in two empirical papers (Part 1 and Part 2), was to replicate and extend the results of previous experiments demonstrating that the body can respond to an emotionally arousing stimulus seconds before it is actually experienced. The second objective, to be presented in a third paper (Part 3), is to develop a theory that explains how the body receives and processes information involved in intuitive perception. DESIGN: The study used a counterbalanced crossover design, in which 30 calm and 15 emotionally arousing pictures were presented to 26 participants under two experimental conditions: a baseline condition of normal psychophysiologic function and a condition of physiological coherence. Primary measures included: skin conductance; the electroencephalogram (EEG), from which cortical event-related potentials and heartbeat-evoked potentials were derived; and the electrocardiogram (ECG), from which cardiac decelerations/accelerations were derived. These measures were used to investigate where and when in the brain and body intuitive information is processed. RESULTS: The study's results are presented in two parts. The main findings in relation to the heart's role in intuitive perception presented here are: (1) surprisingly, the heart appears to receive and respond to intuitive information; (2) a significantly greater heart rate deceleration occurred prior to future emotional stimuli compared to calm stimuli; (3) there were significant gender differences in the processing of prestimulus information. Part 2 will present results indicating where in the brain intuitive information is processed and data showing that prestimulus information from the heart is communicated to the brain. It also presents evidence that females are more attuned to intuitive information from the heart. CONCLUSIONS: Overall, we have independently replicated and extended previous research documenting prestimulus responses. It appears that the heart is involved in the processing and decoding of intuitive information. Once the prestimulus information is received in the psychophysiologic systems, it appears to be processed in the same way as conventional sensory input. This study presents compelling evidence that the body's perceptual apparatus is continuously scanning the future. To account for the results presented in Parts 1 and 2, Part 3 will develop a theory based on holographic principles explaining how intuitive perception accesses a field of energy into which information about future events is spectrally enfolded.     

The role of the basal forebrain in episodic memory retrieval: a positron emission tomography study

Human lesion data indicate that the basal forebrain or orbitofrontal cortex, or both, as well as medial temporal and diencephalic structures, is important for normal memory and that its disruption causes the pure amnesic syndrome, in which episodic memory is grossly impaired while other kinds of memory remain preserved. Among these critical areas, functional imaging studies have so far failed to detect activation of the basal forebrain, although activation in the nearby orbitofrontal cortex has been reported during episodic memory retrieval. We employed positron emission tomography to elucidate the neural basis of episodic memory recall utilizing two types of time cues and successfully detected activity in the basal forebrain for the first time. Specifically, recall of previously memorized words from temporal cues was associated with activity in the basal forebrain, right middle frontal gyrus, right superior temporal gyrus, and posterior cingulate gyrus, whereas their recall from person cues was associated with activity in the left insula, right middle frontal gyrus, and posterior cingulate gyrus. Furthermore, percentage increases of regional blood flow in the basal forebrain were correlated with behavioral data of successful recall. Our results provide clear evidence that the human basal forebrain has a specific role in episodic memory recall, especially that from time-contextual information.     

The effect of visual and auditory enhancements on excitability of the primary motor cortex during motor imagery: a pilot study

The effect of visual and auditory enhancements of finger movement on corticospinal excitability during motor imagery (MI) was investigated using the transcranial magnetic stimulation technique. Motor-evoked potentials were elicited from the abductor digit minimi muscle during MI with auditory, visual and, auditory and visual information, and no information. Ten healthy participants were instructed to imagine repetitive abduction and adduction of the fifth finger. After each condition, the extent of vividness of MI was rated using a visual analogue scale. The results showed that the mean visual analogue scale score and motor-evoked potentials amplitude for the auditory and visual condition were higher than those of other conditions, indicating an enhanced excitability of the primary motor cortex with a clearer image of motor action during MI.