Assessment of sustained and divided attention in rats

Neurorestoration of Sustained Attention in a Model of HIV-1 Associated Neurocognitive Disorders

Due to the sustained prevalence of human immunodeficiency virus (HIV)-1 associated neurocognitive disorders (HAND) in the post-combination antiretroviral therapy (cART) era, as well as the increased prevalence of older HIV-1 seropositive individuals, there is a critical need to develop adjunctive therapeutics targeted at preserving and/or restoring neurocognitive function. To address this knowledge gap, the present study examined the utility of S-Equol (SE), a phytoestrogen produced by gut microbiota, as an innovative therapeutic strategy. A signal detection operant task with varying signal durations (1,000, 500, 100 ms) was utilized to assess sustained attention in HIV-1 transgenic (Tg) and control animals. During the signal detection pretest assessment, HIV-1 Tg animals displayed profound deficits in stimulus-response learning and sustained attention relative to control animals. Subsequently, between 6 and 8 months of age, HIV-1 Tg and control animals were treated with a daily oral dose of either placebo or SE (0.05, 0.1, 0.2 mg) and a posttest assessment was conducted in the signal detection operant task with varying signal durations. In HIV-1 Tg animals, a linear decrease in the number of misses at 100 ms was observed as SE dose increased, suggesting a dose response with the most effective dose at 0.2 mg SE, approximating controls. Comparison of the number of misses across signal durations at the pretest and posttest revealed a preservation of neurocognitive function in HIV-1 Tg animals treated with 0.2 mg SE; an effect that was in sharp contrast to the neurocognitive decline observed in HIV-1 Tg animals treated with placebo. The results support the utility of 0.2 mg SE as a potential efficacious neuroprotective and/or neurorestorative therapeutic for sustained attention, in the absence of any adverse peripheral effects, in the HIV-1 Tg rat. Thus, the present study highlights the critical need for further in vivo studies to elucidate the full potential and generalizability of phytoestrogen treatment for HAND.

Chemogenetic Inactivation of Dorsal Anterior Cingulate Cortex Neurons Disrupts Attentional Behavior in Mouse

Attention is disrupted commonly in psychiatric disorders, yet mechanistic insight remains limited. Deficits in this function are associated with dorsal anterior cingulate cortex (dACC) excitotoxic lesions and pharmacological disinhibition; however, a causal relationship has not been established at the cellular level. Moreover, this association has not yet been examined in a genetically tractable species such as mice. Here, we reveal that dACC neurons causally contribute to attention processing by combining a chemogenetic approach that reversibly suppresses neural activity with a translational, touchscreen-based attention task in mice. We virally expressed inhibitory hM4Di DREADD (designer receptor exclusively activated by a designer drug) in dACC neurons, and examined the effects of this inhibitory action with the attention-based five-choice serial reaction time task. DREADD inactivation of the dACC neurons during the task significantly increased omission and correct response latencies, indicating that the neuronal activities of dACC contribute to attention and processing speed. Selective inactivation of excitatory neurons in the dACC not only increased omission, but also decreased accuracy. The effect of inactivating dACC neurons was selective to attention as response control, motivation, and locomotion remain normal. This finding suggests that dACC excitatory neurons play a principal role in modulating attention to task-relevant stimuli. This study establishes a foundation to chemogenetically dissect specific cell-type and circuit mechanisms underlying attentional behaviors in a genetically tractable species.

Measuring Attention in Rodents: Comparison of a Modified Signal Detection Task and the 5-Choice Serial Reaction Time Task

Neuropsychiatric research has utilized cognitive testing in rodents to improve our understanding of cognitive deficits and for preclinical drug development. However, more sophisticated cognitive tasks have not been as widely exploited due to low throughput and the extensive training time required. We developed a modified signal detection task (SDT) based on the growing body of literature aimed at improving cognitive testing in rodents. This study directly compares performance on the modified SDT with a traditional test for measuring attention, the 5-choice serial reaction time task (5CSRTT). Adult male Sprague-Dawley rats were trained on either the 5CSRTT or the SDT. Briefly, the 5CSRTT required rodents to pay attention to a spatial array of five apertures and respond with a nose poke when an aperture was illuminated. The SDT required the rat to attend to a light panel and respond either left or right to indicate the presence of a signal. In addition, modifications were made to the reward delivery, timing, control of body positioning, and the self-initiation of trials. It was found that less training time was required for the SDT, with both sessions to criteria and daily session duration significantly reduced. Rats performed with a high level of accuracy (>87%) on both tasks, however omissions were far more frequent on the 5CSRTT. The signal duration was reduced on both tasks as a manipulation of task difficulty relevant to attention and a similar pattern of decreasing accuracy was observed on both tasks. These results demonstrate some of the advantages of the SDT over the traditional 5CSRTT as being higher throughput with reduced training time, fewer omission responses and their body position was controlled at stimulus onset. In addition, rats performing the SDT had comparable high levels of accuracy. These results highlight the differences and similarities between the 5CSRTT and a modified SDT as tools for assessing attention in preclinical animal models.

Assessing behavioural and cognitive domains of autism spectrum disorders in rodents: current status and future perspectives

The establishment of robust and replicable behavioural testing paradigms with translational value for psychiatric diseases is a major step forward in developing and testing etiology-directed treatment for these complex disorders. Based on the existing literature, we have generated an inventory of applied rodent behavioural testing paradigms relevant to autism spectrum disorders (ASD). This inventory focused on previously used paradigms that assess behavioural domains that are affected in ASD, such as social interaction, social communication, repetitive behaviours and behavioural inflexibility, cognition as well as anxiety behaviour. A wide range of behavioural testing paradigms for rodents were identified. However, the level of face and construct validity is highly variable. The predictive validity of these paradigms is unknown, as etiology-directed treatments for ASD are currently not on the market. To optimise these studies, future efforts should address aspects of reproducibility and take into account data about the neurodevelopmental underpinnings and trajectory of ASD. In addition, with the increasing knowledge of processes underlying ASD, such as sensory information processes and synaptic plasticity, phenotyping efforts should include multi-level automated analysis of, for example, representative task-related behavioural and electrophysiological read-outs.

Sustained attention in mice: expanding the translational utility of the SAT by incorporating the Michigan Controlled Access Response Port (MICARP)

Advances in mouse genetic technology have spurred increasing interest in the development of cognitive tasks for mice. Here, we describe and discuss the modifications necessary to adapt a task for the assessment of sustained attention performance for use in mice, including for taxing the top-down control of such performance. The validity of the Sustained Attention Task (SAT), including the distractor version (dSAT), has previously been demonstrated in rats and humans. This task requires moveable or retractable operanda; insertion of operanda into the operant chambers cues animals to respond to a prior signal or non-signal event, reporting either a hit or a miss, or a correct rejection or false alarm, respectively. Retractable levers did not support sufficiently high and stable levels of performance in mice. Given the widespread use of static nose-poke devices for testing operant performance in mice, we therefore designed and fabricated a retractable nose-poke device. As this device extends into chambers, a hole for nose-poking is slowly opened and closed again as the device retracts (termed the "Michigan Controlled Access Response Port", MICARP). Results describe the effects of variation of signal duration and event rate, trial outcome and trial type probability, effects of mice deprivation levels, and the reliability of SAT and dSAT performance. Mice perform the SAT and dSAT at levels comparable to those observed in rats. This task will be of assistance in expanding the translational usefulness of the SAT and dSAT.

Cognitive effects of psychotomimetic drugs in rats discriminating number cues

RATIONALE

Deficits in memory and attention are broadly acknowledged during psychosis; however, experiments on modeled psychosis often test working memory without systematic manipulation of attentional demands.

OBJECTIVES

The major research goal was discovering which neurobehavioral processes, attention, or memory contributed more to drug-provoked performance deficits.

MATERIALS AND METHODS

Rats were trained to perform operant ratio discrimination (RD) tasks wherein the number of presses at a rear-wall lever was discriminated using one of two front-wall levers. Effects from four psychotomimetic drugs, the serotonin agonist 2,5-dimethoxy-4-iodoamphetamine, the noncompetitive NMDA-glutamate receptor antagonist phencyclidine (PCP), and two CB1-selective cannabinoid agonists, WIN 55,512-2 and AM 411, were assessed using a signal detection analytical overlay to dissociate cognitive from noncognitive motor and motivational disruptions. Further methods allowed dissociation of attention compromises from mnemonic deficits.

RESULTS

For each test compound, at least one dose elicited decreased RD accuracy without affecting response rates, and task difficulty was shown to be a crucial dictator of accuracy effect specificities. Effects from both PCP and WIN 55,512-2 biased animals to select the response lever conditioned for denser reinforcement. The same two drugs rendered peculiar response patterns in distracter light session components, considering light blinks were included to divert subjects' attention away from task-relevant information. The response patterns determined during distracter components of PCP/WIN testing sessions, counterintuitively, suggest performance enhancement.

CONCLUSION

Comprehensive viewing of RD performance patterns after drug administration indicates that sustained attention and transient information management are significantly impaired during the drug-induced psychosis state, while selective attention is less affected.