In a new article in Science, a group of researchers led by Geraint Rees from University College London, suggest they have a found a neural correlate for introspection. The region of interest is the anterior prefrontal cortex of the brain, which is also implicated in other higher cognitive behaviors like planning, decision-making, social intelligence, and determining predicted outcomes of one’s actions [it is the frontal cortex that was damaged in the infamous case of Phineas Gage].
“Introspection” was measured by having people answer a tough question, and subsequently measure how the result of their answer (right vs wrong) affected their confidence in their own decision making in a series of follow up questions. More introspection meant a correlation between the result of their early answers to their confidence in later ones; in a sense, introspection is the meta-analysis of one’s own thoughts. FMRI data showed that increased gray matter volume in the prefrontal cortex was correlated with high levels of introspection.
Dopamine is a key neurotransmitter released in our brains when we do something rewarding. The dopaminergic system is behind most good feelings we have, and it is also the chemical that is targeted by highly addictive drugs such as cocaine.
To create this beautiful micrograph of dopamine crystals, Spike Walker, who won Thursday evening’s Royal Photographic Society‘s Combined Royal Colleges Medal, shone polarized light at the minute chemical structures. The crystals reflect light at different wavelengths depending on their orientations within the overall chemical structure. According to Walker, using this technique highlights more detail in the crystal structure than regular observation through a microscope.
Some new research just came out in Neuron that is incredibly relevant to the work I do in my lab. The myriad (billions) of granule cells in the cerebellum send their axons, the parallel fibers, to the purkinje cells (pictured below). This junction is of utmost importance…excitation of purkinje cells leads to the inhibition of behavior, whereas as inhibition of the purkinje cells generally leads to motor movement. While common sense and many experiments have shown that movement-inducing inhibition of the purkinje cells (called “Long-Term Depression,” or LTD) is vital for motor learning, new research like this points towards the role of excitation of the purkinje cells (called “Long-Term Potentiation,” or LTP), and thus inhibition of motor behavior, as well. I study motor learning in the Medina lab at Upenn, with a focus on the parallel fiber-purkinje cell synapse. This research certainly adds more to the puzzle of motor learning…the mystery grows…
Check out the “video abstract” at http://www.cell.com/neuron/
image/Ramon y Cajal
No two neurons are the same. Even neurons of the same type (i.e. purkinje cells) behave differently. This fact is often overlooked as an important functional feature of the brain, and instead chalked up to biological impreciseness. In their recent Nature article, Krishnan Padmanabhan and Nathaniel Urban think there’s an important reason behind all the diversity. They studied the “intrinsic differences” in the molecular signatures and firing behaviors of mitral cells in the mouse olfactory bulb, and by differentially stimulating different cells concluded that:
Although a number of mechanisms have been proposed to account for the origin and extent of these intrinsic differences, we found that differences in intrinsic biophysical heterogeneity can be important [for] neural coding.
In other words, the intrinsic differences between neurons are not biological mistakes – they are adaptive functions for the complex neural coding of stimulus information.
100 billion neurons, and each one is functionally different? I’m having trouble coding that one…
A review published last week by two Swiss neuroscientists in Nature Neuroscience argues that psychedelic drugs, like psilocybin (“mushrooms”) and LSD, have serious therapeutic applications:
“Recent behavioural and neuroimaging data show that psychedelics modulate neural circuits that have been implicated in mood and affective disorders, and can reduce the clinical symptoms of these disorders (Vollenweider & Kometer, 2010).”
Psychedelics have strong effects on the brain’s glutamatergic and serotonergic pathways, which malfunction in patients with clinical depression and anxiety. Many lines of evidence show that psychedelics can alleviate the symptoms of depression and anxiety using relatively small doses. There are obvious political hurdles to be mounted for any of these drugs to make there way into more research labs, and potentially into pharmacies, but the recent relative success of medical marijuana campaigns may have laid important tracks for thorough research on the positive effects of “taboo” drugs.