Nimodipine Decreases Frontal and Parietal Cortical Activity During Working Memory in Healthy Subjects
At a recent scientific meeting, researcher Kristin Bigos and colleagues described the effects of nimodipine, a treatment for brain hemorrhage, on the brain during working memory tasks. Nimodipine is a dihydropyridine L-type calcium channel blocker. Calcium channel blockers prevent calcium from entering cells in the heart and blood vessel walls, and they are often used to treat high blood pressure.
Nimodipine acts on the CACNA1C calcium influx gene. Certain genetic variations in this gene (particularly the rs1006737 A allele) have been linked to vulnerability to bipolar disorder, schizophrenia, depression, and autism. Carriers of the risk allele also have higher CACNA1C mRNA expression in the dorsolateral prefrontal cortex and exhibit more activity in the frontal and parietal regions of the brain during working memory tasks, suggesting inefficient brain processing in these regions. Bigos and colleagues found that 60mg/day of nimodipine decreased frontal and parietal cortical activity by 39.1% and 42.8%, respectively, during a working memory task, suggesting that nimodipine improved the efficiency of memory processing. Nimodipine’s positive effects were greater in those participants who had the CACNA1C risk allele.
Editor’s Note: Using a placebo-controlled off-on-off-on study design (meaning patients took placebo for a period, then nimodipine, then placebo again and nimodipine again), this editor (Robert M. Post), Peggy J. Pazzaglia and colleagues found that nimodipine had positive effects in both mania and depression in patients with bipolar disorder (described in the 2008 book Treatment of Bipolar Disorder: A Casebook for Clinicians and Patients by Robert M. Post and Gabriele S. Leverich). In a large randomized study of patients with bipolar disorder presented by Haroon R. Chaudhry at the 2010 meeting of the Society of Biological Psychiatry, lithium was associated with about a 50% response rate while the combination of lithium and nimodipine was associated with a 73% response rate.
It remains to be seen whether people with bipolar disorder who have the CACNA1C risk gene would respond better to nimodipine than those without the risk gene, and whether it would improve working memory more in the subgroup with the risk gene.
Antioxidant N-Acetylcysteine Improves Working Memory in Patients with Psychosis
In a 2017 article in the journal Psychological Medicine, researcher Marta Rapado-Castro and colleagues reported that among 58 patients with bipolar disorder or schizophrenia and symptoms of psychosis, those who took two grams per day of the antioxidant n-acetylcysteine (NAC) showed improvements in working memory after six months compared to those who took placebo over the same study period.
Antipsychotic medications can typically reduce psychotic symptoms such as delusions or hallucinations, but cognitive symptoms such as problems with learning, memory, or information processing may remain. NAC, which is sold over-the-counter as a nutritional supplement, seemed to improve these symptoms.
The researchers suggest that larger studies of NAC are needed, particularly to determine whether giving NAC to patients during their first episode of psychosis could prevent cognitive decline from occurring at all during the course of their illness.
NAC has been found to have a range of benefits, including reducing substance abuse and interfering with habit-based behaviors such as compulsive hair-pulling, obsessive-compulsive disorder, and gambling.
Researcher Michael Berk, a co-author of the study, reported in the journal Biological Psychiatry in 2008 that NAC could also improve depressive symptoms in bipolar disorder and negative symptoms in schizophrenia.
Editor’s Note: Since cognitive deficits are common in both schizophrenia and bipolar disorder, using NAC in addition to antipsychotic medications could be a useful tool to address these types of symptoms.
Following Collisions, High School Football Players with No Signs of Concussion May Still Have Neurological Impairment
In a small 2014 study in the Journal of Neurotrauma, researcher Thomas M. Talavaga and colleagues reported that repeated head trauma that did not produce concussion symptoms was still associated with neurocognitive and neurophysiological changes to the brain in high school football players.
The longitudinal study tracked ‘collision events’ experienced by 11 teens who played football at the same high school. The young men also completed neurocognitive testing and magnetic resonance imaging (MRI) scans of their brains over time.
The researchers expected to see the participants fall into two categories: those who had no concussions and normal neurological function, and those who had at least one concussion and subsequent neurological changes. They ended up observing a third group: young men who had not exhibited concussion symptoms, but nonetheless had measurable changes to their neurological functioning, including impairments to visual working memory and altered activation of the dorsolateral prefrontal cortex. Young men in this last group had had more collisions that impacted the top front of the head, directly above the dorsolateral prefrontal cortex.
The authors suggest that the discovery of this third category mean that some neurological injuries are going undetected in high school football players. The players who are injured in this way are not likely to seek treatment, and may continue playing football, risking more neurological brain injury or brain damage with subsequent collisions.
Single Dose of Modafinil Improved Memory in People in Remission from Depression
Modafinil is a wake-promoting medication used to treat narcolepsy, but studies have also shown that it can improve cognition in people with schizophrenia or attention deficit hyperactivity disorder. It may also help people with lingering cognitive difficulties after recovering from a depression. A 2016 article in the journal Biological Psychiatry reported that a single 200mg dose of modafinil improved performance on tests of episodic memory and working memory (but not planning or attention).
The study by researcher Barbara Sahakian and colleagues included 60 patients who had recently recovered from a depression. They took some cognitive tests to establish a baseline of their performance. A week later, they were given either a placebo or a single dose of modafinil, and two hours later they completed the cognitive tests again. The modafinil group performed better on the memory-related tasks.
While side effects were limited, two participants who received modafinil had sleep disturbances that night.
Longer-term studies are needed to determine whether modafinil is safe and effective if taken over a longer period of time. Cognitive dysfunction can interfere with daily tasks such as work or school and put people at greater risk of relapse, so effective treatments have the potential to greatly improve quality of life for people in remission from depression.
Kynurenine Pathway Suggests How Inflammation is Linked to Schizophrenia
The kynurenine pathway describes the steps that turn the amino acid tryptophan (the ingredient in turkey that might make you sleepy) into nicotinamide adenine dinucleotide. This pathway might be a connection between the immune system and neurotransmitters involved in schizophrenia.
A recent autopsy study by researcher Thomas Weickert and colleagues explored this link by determining that in the brains of people with schizophrenia and high levels of inflammation, messenger RNA for Kynurenine Aminotransferase II (KATII, a step on the kynurenine pathway) was elevated in the dorsolateral prefrontal cortex compared to the brains of people who died healthy and those with schizophrenia but low levels of inflammation.
The KATII mRNA levels also correlated with mRNA levels of inflammatory markers such as glial fibrillary acidic protein and interleukin-6.
Blood measures related to the kynurenine pathway also differentiated people with schizophrenia from healthy controls. People with schizophrenia had lower levels of tryptophan, kynurenine, and kynurenic acid in their blood. The low levels of kynurenic acid in the blood were correlated with deficits in working memory and smaller volume of the dorsolateral prefrontal cortex.
Weickert and colleagues suggest that blood levels of kynurenic acid might provide a measurable indicator of the degree to which people with schizophrenia are experiencing problems with executive functioning (planning and decision-making) and loss of brain volume.
Transcranial Direct Current Stimulation May Improve Cognition in Schizophrenia
A recent study by Robert Smith and colleagues studied the use of transcranial direct current stimulation (tDCS) in patients with schizophrenia. TDCS is very low level current that has a positive (anode) or negative (cathode) electrode. Anodal stimulation of the cortex is usually associated with positive effects on mood and cognition. Patients received either five sessions of active tDCS for 20 minutes (at 2 milli Amps) or a sham stimulation for the same period. Then, one day after the final session, the patients were measured on a variety of scales for cognition and illness. Patients who received the active tDCS showed more improvements in working memory and attention than patients who received the sham treatment.
There was no difference in the two groups’ schizophrenic symptoms, including hallucinations. Smith and colleagues suggest that the improvements in cognition may result from changes to brain connectivity networks, since abnormalities in these networks have been identified in patients with schizophrenia and bipolar disorder.
Replications of this type of study are needed to clarify the effect of tDCS on cognition in schizophrenia, but given the safety and convenience of the procedure, the findings are promising.
RTMS Improves Working Memory In Patients With Schizophrenia
Repetitive transcranial magnetic stimulation (rTMS) may improve working memory in patients with schizophrenia, according to a small study published by Zafiris J. Daskalakis and colleagues in Biological Psychiatry in 2013. Patients with schizophrenia received either 20 Hz rTMS over the left and right prefrontal cortex or a sham treatment, and the rTMS improved working memory on a particular task, the n-back task, wherein patients are asked to recall whether a stimulus they’re currently viewing is the same as the previous one they viewed, or one they viewed several times back. Twenty sessions of rTMS over a period of 4 weeks brought memory back to the levels seen in normal controls.
Editor’s Note: Since many patients with bipolar disorder also have deficits in prefrontal-based memory and performance even when euthymic, it will be important to see if rTMS would also be helpful in these patients. RTMS at 20 Hz increases neuronal activity as measured by PET scan of the prefrontal cortex and other regions of the brain, and this lasts for at least 48 hours after each treatment.
Since many patients with schizophrenia and bipolar disorder show deficits in prefrontal activity at baseline, the normalization of these alterations could relate to the memory improvement. This proposition could be tested relatively easily.
