Distinct functional connectivity of the hippocampus during semantic and phonemic fluency

Glikmann‐Johnston, Yifat; Oren, Noga; Hendler, Talma; Shapira‐Lichter, Irit

doi:10.1016/j.neuropsychologia.2015.01.031

Cited by 49 publications

(37 citation statements)

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“…Some authors suggested that the involvement of left hippocampus in semantic information processing result from use of strategies relying on autobiographic processes and episodic recollections optimizing semantic memory functioning [39,41–43]. Recent studies have highlighted a selective recruitment of the hippocampus in verbal fluency tasks, particularly in semantic ones [38,39,44–46]. …”

Section: Discussionmentioning

confidence: 99%

Patterns of brain atrophy associated with episodic memory and semantic fluency decline in aging

Pelletier

Bernard

Dilharreguy

et al. 2017

Aging

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The cerebral substratum of age-related cognitive decline was evaluated in an elderly-cohort followed for 12 years (n=306). Participants, free of dementia, received neuropsychological assessments every two years and an MRI exam at baseline and four years later. Cognitive decline was evaluated on two broadly used tests to detect dementia: the Free and Cued Selective Reminding Test (FCSRT), a verbal episodic memory task, and the Isaacs Set Test (IST), a semantic fluency task. Using voxel-based approach, the relationship between cognitive decline with 1/ baseline grey matter volumes and 2/ grey matter volume loss between the two scans was explored. Baseline volumes analysis revealed that FCSRT and IST declines were both associated with lower volumes of the medial temporal region. Volumes loss analysis confirmed that both declines are related to medial temporal lobe atrophy and revealed that FCSRT decline was specifically associated with atrophy of the posterior cingulate cortex whereas IST decline was specifically related to temporal pole atrophy. These results suggest that cognitive decline across aging is firstly related to structural modifications of the medial temporal lobe, followed by an atrophy in the posterior midline structures for episodic memory and an atrophy of the temporal pole for semantic fluency.

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Section: Discussionmentioning

confidence: 99%

Patterns of brain atrophy associated with episodic memory and semantic fluency decline in aging

Pelletier

Bernard

Dilharreguy

et al. 2017

Aging

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“…81 Therefore, although VF has traditionally been viewed as a 'frontal' function, it involves a memory network, and a recent fMRI study found hippocampal connectivity with a semantic network during semantic (category), but not phonetic (letter), fluency. 82 VF is strongly impaired by ECT, whereas WM is relatively unaffected by ECT. 17 Semantic VF is therefore a possible functional probe of the associative memory network, which includes the hippocampus, and is sensitive to the effects of ECT, whereas WM tasks appear more restricted to a cortical network that is less affected.…”

Section: Assessment Of Frontal Cortex Function: the Use Of Near Inframentioning

confidence: 87%

Randomised controlled trial of ketamine augmentation of electroconvulsive therapy to improve neuropsychological and clinical outcomes in depression (Ketamine-ECT study)

et al. 2017

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BackgroundElectroconvulsive therapy (ECT) is the most effective acute treatment for severe depression, but there are concerns about its adverse cognitive effects. ECT may impair cognition through stimulation of glutamate receptors, and preliminary evidence has suggested that ketamine, a glutamate antagonist, may alleviate these effects. Ketamine has been shown to have a rapid, but temporary, antidepressant effect after a single infusion.ObjectiveTo determine the efficacy and safety of adjunctive low-dose ketamine to reduce cognitive impairments caused by ECT and, secondarily, to improve symptomatic outcome.DesignMulticentre, two-arm, parallel-group, patient-randomised, placebo-controlled superiority trial.SettingEleven ECT suites based in seven NHS trusts in the north of England.ParticipantsSeverely depressed hospitalised patients or outpatients who received ECT as part of their usual clinical care.InterventionsPatients were randomised to ketamine (0.5 mg/kg) or saline as an adjunct to their anaesthetic for their ECT course in a 1 : 1 ratio.Main outcome measuresThe primary outcome was delayed verbal recall on the Hopkins Verbal Learning Task – Revised (HVLT-R) after four ECT treatments (mid-ECT), analysed using a Gaussian repeated measures model. Secondary outcomes included autobiographical, working and visual memory and verbal fluency, symptoms and quality of life; assessments occurred at mid-ECT, end of treatment and 1 and 4 months after the last ECT. Neuropsychological function was compared with that of healthy control subjects and a functional near-infrared spectroscopy (fNIRS) substudy investigated prefrontal cortex function. A patient survey of study participation was carried out.ResultsSeventy-nine severely depressed patients were randomised to ketamine (0.5 mg/kg) or saline as an adjunct to their anaesthetic for their ECT course; the modified intention-to-treat sample included 70 patients. Compared with saline, adjunctive ketamine had no significant effect on HVLT-R delayed recall [treatment effect difference –0.43, 95% confidence interval (CI) –1.73 to 0.87], other neuropsychological outcomes, improvement in depression [difference in Montgomery–Åsberg Depression Rating Scale (MADRS) score of 0.44, 95% CI –1.03 to 1.91], the number of ECT treatments to remission (MADRS score of ≤ 10: 0.83, 95% CI –3.2 to 4.9), anxiety symptoms or quality of life. By the end of ECT treatment, 37% (saline 35%, ketamine 39%) of patients had remitted. Tolerability was similar in the two treatment arms; two patients had isolated transient psychological effects attributable to ketamine. Preliminary fNIRS analysis found that patients had blunted prefrontal cortical haemodynamic responses compared with control subjects during a verbal fluency task at baseline; this was further diminished at mid-ECT without modulation by ketamine. Greater haemodynamic responsivity to ECT appeared to be associated with a better clinical response. The majority of patients surveyed reported a positive experience of study participation.ConclusionsThe results of the study do not support the use of adjunctive ketamine in routine ECT treatment in the NHS. Although no evidence of benefit was found for ketamine, moderate benefits or harms cannot be excluded, as recruitment was < 50% of that planned, limiting the power of the clinical trial. Low numbers also meant that in the fNIRS substudy the effect of ketamine could not be assessed and the other findings must be viewed as preliminary. Included patients were younger than those not included and had only limited cognitive impairment with ECT, limiting generalisation to more cognitively compromised patients. fNIRS appeared to be a potentially feasible portable brain imaging technology in severely ill patients and further research is warranted to investigate its clinical utility.Trial registrationCurrent Controlled Trials ISRCTN14689382.FundingThis project was funded by the Efficacy and Mechanism Evaluation programme, a Medical Research Council and National Institute for Health Research partnership.

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“…Here, we did not individualize these different subdomains of apathy, but we found that apathetic iNPH patients improved their STV after CSF tapping in a specific dual‐task condition (walking and enumerating animal names) that is associated with executive functioning—this better improvement was also found for gait speed, but not for stride time and stride length. Interestingly, verbal fluency tasks—phonemic and categorical—are associated with separate frontal networks, and unlike phonemic verbal fluency, bilateral hippocampi are selectively involved in the brain networks that supports categorical verbal fluency . CSF tapping decreases the surrounding pressure around the ventricles not only in the frontal regions but also in the hippocampi, specifically involved in higher level of gait control—hippocampal volume has been associated with gait performance in older adults.…”

Section: Discussionmentioning

confidence: 99%

Apathy in idiopathic normal pressure hydrocephalus: A marker of reversible gait disorders

Allali

Laidet

Armand

et al. 2018

Int J Geriat Psychiatry

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Objective: Apathy-the most common behavioral disturbance in idiopathic normal pressure hydrocephalus (iNPH)-is associated with poor gait, but the role of apathy on gait improvement after cerebrospinal fluid (CSF) tapping has not been studied yet. This study aims to compare gait improvement after CSF tapping in iNPH patients with and without apathy.Methods: Stride time variability (STV), a marker of higher level of gait control, was measured in 33 iNPH patients (78.4 ± 5.7 years; 36.4% women) with an optoelectronic system during usual walking (single task) and during walking while dual tasking of counting and verbal fluency before and 24 hours after CSF tapping. Apathy was defined by a score ≥14 on the Starkstein apathy scale.Results: Apathy was present in 60.6% of patients. Cerebrospinal fluid tapping led to greater improvement of STV (ie, decrease) during dual-task walking (and more specifically categorical verbal fluency) in apathetic compared to nonapathetic patients (−44.7 ± 58.1% versus +4.24 ± 67.6%, respectively; P = .040), even after adjusting for age and depressive symptoms.More severe apathy was correlated with better STV improvement while dual tasking (categorical verbal fluency) after CSF tapping (r = −0.412; P-value = 0.021), while it was not correlated with improvement on executive tests. Conclusions:Our findings suggest that the presence of apathy is a predictor of better outcomes of gait disorders after CSF tapping in patients with iNPH.

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Distinct functional connectivity of the hippocampus during semantic and phonemic fluency

Cited by 49 publications

References 56 publications

Patterns of brain atrophy associated with episodic memory and semantic fluency decline in aging

Patterns of brain atrophy associated with episodic memory and semantic fluency decline in aging

Randomised controlled trial of ketamine augmentation of electroconvulsive therapy to improve neuropsychological and clinical outcomes in depression (Ketamine-ECT study)

Apathy in idiopathic normal pressure hydrocephalus: A marker of reversible gait disorders

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