Mice expressing P301S mutant human tau have deficits in interval timing

Complementary cognitive roles for D2-MSNs and D1-MSNs in interval timing

The role of striatal pathways in cognitive processing is unclear. We studied dorsomedial striatal cognitive processing during interval timing, an elementary cognitive task that requires mice to estimate intervals of several seconds, which involves working memory for temporal rules as well as attention to the passage of time. We harnessed optogenetic tagging to record from striatal D2-dopamine receptor-expressing medium spiny neurons (D2-MSNs) in the indirect pathway and from D1-dopamine receptor-expressing MSNs (D1-MSNs) in the direct pathway. We found that D2-MSNs and D1-MSNs exhibited opposing dynamics over temporal intervals as quantified by principal component analyses and trial-by-trial generalized linear models. MSN recordings helped construct and constrain a four-parameter drift-diffusion computational model. This model predicted that disrupting either D2-MSN or D1-MSNs would increase interval timing response times and alter MSN firing. In line with this prediction, we found that optogenetic inhibition or pharmacological disruption of either D2-MSNs or D1-MSNs increased response times. Pharmacologically disrupting D2-MSNs or D1-MSNs also increased response times, shifted MSN dynamics, and degraded trial-by-trial temporal decoding. Together, our findings demonstrate that D2-MSNs and D1-MSNs make complementary contributions to interval timing despite opposing dynamics, implying that striatal direct and indirect pathways work together to shape temporal control of action. These data provide novel insight into basal ganglia cognitive operations beyond movement and have implications for a broad range of human striatal diseases and for therapies targeting striatal pathways.

Alpha-Synuclein Pre-Formed Fibrils Injected into Prefrontal Cortex Primarily Spread to Cortical and Subcortical Structures

BACKGROUND

Parkinson's disease dementia (PDD) and dementia with Lewy bodies (DLB) are characterized by diffuse spread of alpha-synuclein (α-syn) throughout the brain. Patients with PDD and DLB have a neuropsychological pattern of deficits that include executive dysfunction, such as abnormalities in planning, timing, working memory, and behavioral flexibility. The prefrontal cortex (PFC) plays a major role in normal executive function and often develops α-syn aggregates in DLB and PDD.

OBJECTIVE

To investigate the long-term behavioral and cognitive consequences of α-syn pathology in the cortex and characterize pathological spread of α-syn.

METHODS

We injected human α-syn pre-formed fibrils into the PFC of wild-type male mice. We then assessed the behavioral and cognitive effects between 12- and 21-months post-injection and characterized the spread of pathological α-syn in cortical, subcortical, and brainstem regions.

RESULTS

We report that PFC PFFs: 1) induced α-syn aggregation in multiple cortical and subcortical regions with sparse aggregation in midbrain and brainstem nuclei; 2) did not affect interval timing or spatial learning acquisition but did mildly alter behavioral flexibility as measured by intraday reversal learning; and 3) increased open field exploration.

CONCLUSIONS

This model of cortical-dominant pathology aids in our understanding of how local α-syn aggregation might impact some symptoms in PDD and DLB.

Alpha-synuclein pre-formed fibrils injected into prefrontal cortex primarily spread to cortical and subcortical structures and lead to isolated behavioral symptoms

Parkinson's disease dementia (PDD) and dementia with Lewy bodies (DLB) are characterized by diffuse spread of alpha-synuclein (α-syn) throughout the brain. Patients with PDD and DLB have a neuropsychological pattern of deficits that include executive dysfunction, such as abnormalities in planning, timing, working memory, and behavioral flexibility. The prefrontal cortex (PFC) plays a major role in normal executive function and often develops α-syn aggregates in DLB and PDD. To investigate the consequences of α-syn pathology in the cortex, we injected human α-syn pre-formed fibrils into the PFC of wildtype mice. We report that PFC PFFs: 1) induced α-syn aggregation in multiple cortical and subcortical regions with sparse aggregation in midbrain and brainstem nuclei; 2) did not affect interval timing or spatial learning acquisition but did mildly alter behavioral flexibility as measured by intraday reversal learning; 3) increased open field exploration; and 4) did not affect susceptibility to an inflammatory challenge. This model of cortical-dominant pathology aids in our understanding of how local α-syn aggregation might impact some symptoms in PDD and DLB.

Sex similarities and dopaminergic differences in interval timing

Rodent behavioral studies have largely focused on male animals, which has limited the generalizability and conclusions of neuroscience research. Working with humans and rodents, we studied sex effects during interval timing that requires participants to estimate an interval of several seconds by making motor responses. Interval timing requires attention to the passage of time and working memory for temporal rules. We found no differences between human females and males in interval timing response times (timing accuracy) or the coefficient of variance of response times (timing precision). Consistent with prior work, we also found no differences between female and male rodents in timing accuracy or precision. In female rodents, there was no difference in interval timing between estrus and diestrus cycle stages. Because dopamine powerfully affects interval timing, we also examined sex differences with drugs targeting dopaminergic receptors. In both female and male rodents, interval timing was delayed after administration of sulpiride (D2-receptor antagonist), quinpirole (D2-receptor agonist), and SCH-23390 (D1-receptor antagonist). By contrast, after administration of SKF-81297 (D1-receptor agonist), interval timing shifted earlier only in male rodents. These data illuminate sex similarities and differences in interval timing. Our results have relevance for rodent models of both cognitive function and brain disease by increasing represenation in behavioral neuroscience.

Glycolysis-enhancing α1-adrenergic antagonists modify cognitive symptoms related to Parkinson's disease

Terazosin is an α1-adrenergic receptor antagonist that enhances glycolysis and increases cellular ATP by binding to the enzyme phosphoglycerate kinase 1 (PGK1). Recent work has shown that terazosin is protective against motor dysfunction in rodent models of Parkinson's disease (PD) and is associated with slowed motor symptom progression in PD patients. However, PD is also characterized by profound cognitive symptoms. We tested the hypothesis that terazosin protects against cognitive symptoms associated with PD. We report two main results. First, in rodents with ventral tegmental area (VTA) dopamine depletion modeling aspects of PD-related cognitive dysfunction, we found that terazosin preserved cognitive function. Second, we found that after matching for demographics, comorbidities, and disease duration, PD patients newly started on terazosin, alfuzosin, or doxazosin had a lower hazard of being diagnosed with dementia compared to tamsulosin, an α1-adrenergic receptor antagonist that does not enhance glycolysis. Together, these findings suggest that in addition to slowing motor symptom progression, glycolysis-enhancing drugs protect against cognitive symptoms of PD.

Novel Strategy for Alzheimer’s Disease Treatment through Oral Vaccine Therapy with Amyloid Beta

Alzheimer’s disease (AD) is a neuropathology characterized by progressive cognitive impairment and dementia. The disease is attributed to senile plaques, which are aggregates of amyloid beta (Aβ) outside nerve cells; neurofibrillary tangles, which are filamentous accumulations of phosphorylated tau in nerve cells; and loss of neurons in the brain tissue. Immunization of an AD mouse model with Aβ-eliminated pre-existing senile plaque amyloids and prevented new accumulation. Furthermore, its effect showed that cognitive function can be improved by passive immunity without side effects, such as lymphocyte infiltration in AD model mice treated with vaccine therapy, indicating the possibility of vaccine therapy for AD. Further, considering the possibility of side effects due to direct administration of Aβ, the practical use of the safe oral vaccine, which expressed Aβ in plants, is expected. Indeed, administration of this oral vaccine to Alzheimer’s model mice reduced Aβ accumulation in the brain. Moreover, almost no expression of inflammatory IgG was observed. Therefore, vaccination prior to Aβ accumulation or at an early stage of accumulation may prevent Aβ from causing AD.