Involvement of middle temporal area (MT) in the processing of chromatic motion

We recorded single-neuron and multi-unit activity in cortical motion-processing area MT (V5) of anaesthetized paralyzed macaque monkeys in response to moving sinewave gratings modulated in both luminance and chromatic domain. The activity of MT neurons was highly dependent on luminance contrast. In 3 of 4 animals we found (isoluminant) modulations that did not activate any neuron. With the equivalent visual stimuli, in contrast, speed judgments and onset parameters of evoked optokinetic eye movements in human subjects were largely independent of luminance modulation. Motion of every grating (including isoluminant) was readily visible for all but one observer. Our results do not suggest a critical role of area MT in the processing of chromatic motion and do not support the idea of MT as a universal substrate for visual motion representation in the primate cerebral cortex

The Evidence for Altered BDNF Expression in the Brain of Rats Reared or Housed in Social Isolation: A Systematic Review

There is evidence that development and maintenance of neural connections are disrupted in major mental disorders, which indicates that neurotrophic factors could play a critical role in their pathogenesis. Stress is a well-established risk factor for psychopathology and recent research suggests that disrupted signaling via brain-derived neurotrophic factor (BDNF) may be involved in mediating the negative effects of stress on the brain. Social isolation of rats elicits chronic stress and is widely used as an animal model of mental disorders such as schizophrenia and depression. We carried out a systematic search of published studies to review current evidence for an altered expression of BDNF in the brain of rats reared or housed in social isolation. Across all age groups (post-weaning, adolescent, adult), majority of the identified studies (16/21) reported a decreased expression of BDNF in the hippocampus. There are far less published data on BDNF expression in other brain regions. Data are also scarce to assess the behavioral changes as a function of BDNF expression, but the downregulation of BDNF seems to be associated with increased anxiety-like symptoms. The reviewed data generally support the putative involvement of BDNF in the pathogenesis of stress-related mental illness. However, the mechanisms linking chronic social isolation, BDNF expression and the elicited behavioral alterations are currently unknown

Differential effects of executive load on automatic versus controlled semantic memory retrieval

Growing evidence indicates that a domain-general executive control supports semantic memory retrieval, yet the nature of this interaction remains elusive. To shed light on such control mechanisms, we conducted two dual-task experiments loading distinct executive capacities (working memory maintenance, monitoring, and switching), while participants carried out automatic (free-associative) and controlled (dissociative) word retrieval tasks. We found that these forms of executive load interfered with retrieval fluency in both tasks, but these negative effects were more pronounced for the dissociative performance. Together, these findings indicate that the domain-general executive control supports accessing contextually relevant knowledge as well as the inhibition of automatically activated but task-inappropriate retrieval candidates, putatively via an adaptive gating of semantic activation and interference control. Moreover, the processing costs related to retrieval inhibition and switching were negatively correlated, suggesting a tradeoff between the ability to constrain semantic activation (i.e., inhibition) and the ability to initiate flexible transitions between semantic sets (i.e., switching), which may thus represent two complementary control functions governing semantic memory retrieval

Time-dependent involvement of controlled processing in semantic retrieval

Growing evidence indicates that retrieval in semantic verbal fluency (SVF) gets more effortful over time, putatively, as progressively less typical and weakly connected retrieval candidates are being retrieved. Nevertheless, the dynamic involvement of controlled processes across the stages of continuous SVF performance is poorly understood. To address this issue, we will conduct an experimental study investigating whether and how individual variability in multiple-demand and semantic-specific cognitive control predicts retrieval performance across distinct stages of SVF, while also manipulating the semantic difficulty of the categories. We believe that addressing this objective will bring major implications for the current models of semantic cognition as well as the use of SVF in both neurotypical and clinical individuals

Executive functioning moderates the decline of retrieval fluency in time

This is the data repository for the article titled "Executive functioning moderates the decline of retrieval fluency in time" accepted for publication in Psychological Research (2022

Executive functioning moderates the decline of retrieval fluency in time

Prevailing theoretical accounts consider that automatic and controlled processes are uniformly engaged in memory retrieval across performance of the semantic verbal fluency (SVF) task. We tested this proposal against the alternative, namely that a rapid automatic retrieval, exploiting stable associative structure in the early stages of the performance, is followed by a slower, more executively demanding, retrieval in later stages. Eighty-five healthy adults completed low- and high-demand SVF tasks that were assessed for retrieval rate, response typicality, and inter-response similarity across the performance. Additional measures of executive functioning were collected to estimate individual differences in executive control. We found that decrease in fluency in time was associated with lower typicality and weaker semantic similarity of the responses. Critically, the time-dependent retrieval slowing was steeper in individuals with less efficient interference control, particularly in high-demand SVF tasks. Steeper retrieval slowing was also associated with poorer working-memory capacity. Our findings show that the relative contribution of automatic and controlled processes to semantic retrieval changes with associative sparsity over time and across task demands, and provide implications for the use of SVF tasks in clinical assessment

Measuring semantic memory using associative and dissociative retrieval tasks

The study introduces the Associative-Dissociative Retrieval Task (ADT), developed to assess the automatic (free–associative) and controlled (dissociative/inhibitory) semantic memory functions, detailing its theoretical background and psychometric characteristics. Based on data from 102 healthy young adults who completed three parallel forms of the task, we show that retrieving semantically dissociated concepts requires substantially more time than delivering free associations, providing support for elevated processing demands on inhibition. Moreover, the retrieval latencies in the two retrieval conditions, and their difference (i.e., the inhibition cost), were identical and strongly correlated across the parallel forms, confirming excellent reliability, homogeneity, and short-term temporal stability of the ADT measures. Furthermore, we created a set of 120 standard word stimuli and assessed their psycholinguistic and associative features to identify those influencing the retrieval performance, enabling other researchers to tailor item selection according to their needs. This in-depth stimulus-level analysis revealed that retrieving related concepts is easier for words that evoke few but strong associates (i.e., high potency stimuli), yet such propensity may hamper the inhibition. The construct validity of the ADT measures was further supported by subsequent analyses demonstrating moderate to strong correlations with measures assessing semantic processing and long-term memory retrieval (semantic verbal fluency and associative combination) but non-significant or weak correlations with domain-general cognitive capacities (processing speed and working memory). These findings allow us to conclude that ADT provides simple yet potent and psychometrically sound measures of semantic memory retrieval that bear several noteworthy features and potential advantages over the currently available assessment methods

Measuring semantic memory using associative and dissociative retrieval tasks

Data, materials, and codes used in the study