If serotonin deficiency isn’t the cause of depression, then why do SSRIs work?

Acetaminophen (a.k.a paracetamol) relieves some types of headache. But this does not mean that these headaches are caused by acetaminophen deficiency. The brain doesn’t even produce acetaminophen.

The point of this analogy is to make clear that a medicine can work even if it is not acting on the cause of the symptom. In many cases a medicine can work even when the cause of the symptom is completely unknown.

Continue reading

Less is more? A strange case of improvement in intelligence & personality after removal of prefrontal cortical tissue!

While reading a paper on the neuroscience of dreaming I came across a reference to a 1940 paper by Donald Hebb and Wilder Penfield. It’s a neurosurgery case study that is quite stunning. It shows that in some cases, removal of prefrontal brain tissue can actually cause improvements in intelligence and personality. So basically it’s the opposite of the Phineas Gage story.

Here are some excerpts from the paper:

Hebb1.png

Continue reading

Why is the brain so sensitive to early life experiences?

I was asked this question on Quora:

From an evolutionary standpoint, why would the early years of brain development be paramount in determining life-long neurological patterns, when those patterns can often be detrimental to long-term success in life?

Good question. We can restate it as follows:

Why would natural selection allow animals to be so sensitive to negative early experience?

Continue reading

The neural circuitry of emotion – an interview with me!

I was interviewed by the excellent Allen Saakyan for his Simulation YouTube channel. Check it out if you want to know about my research… and also my take on the question of Life, the Universe, and Everything. 😛

There’s also a shorter excerpt where we speculate about schizophrenia and “hyperrealities”:

Our computational model of visual attention disruptions in schizophrenia

My latest modeling paper has been published in Computational Psychiatry.

Visual Attention Deficits in Schizophrenia Can Arise From Inhibitory Dysfunction in Thalamus or Cortex (Open Access!)

Here’s the abstract:

“Schizophrenia is associated with diverse cognitive deficits, including disorders of attention-related oculomotor behavior. At the structural level, schizophrenia is associated with abnormal inhibitory control in the circuit linking cortex and thalamus. We developed a spiking neural network model that demonstrates how dysfunctional inhibition can degrade attentive gaze control. Our model revealed that perturbations of two functionally distinct classes of cortical inhibitory neurons, or of the inhibitory thalamic reticular nucleus, disrupted processing vital for sustained attention to a stimulus, leading to distractibility. Because perturbation at each circuit node led to comparable but qualitatively distinct disruptions in attentive tracking or fixation, our findings support the search for new eye movement metrics that may index distinct underlying neural defects. Moreover, because the cortico-thalamic circuit is a common motif across sensory, association, and motor systems, the model and extensions can be broadly applied to study normal function and the neural bases of other cognitive deficits in schizophrenia.”

Here’s Figure 1, which shows the circuit we modeled.

“the term reward has no consistent meaning”

A very important point about dopamine (DA) and reward, from a recent review paper:

“The DA hypothesis of reward is a ubiquitous feature of the scientific literature, as well as popular media, the internet, and film. Yet, despite the almost automatic tendency of some to explain virtually any aspect of DA function as somehow being dependent on reward, there are critical theoretical and empirical problems with this, many of which have been reviewed in detail elsewhere (Salamone et al., 1997, 2007; Salamone and Correa, 2002, 2012; Floresco, 2015; Nicola, 2016). First and foremost, the term reward has no consistent scientific meaning (Salamone et al., 2005; Salamone and Correa, 2012), and, depending upon the paper, or even the paragraph, this term is used variously to refer to subjective pleasure or hedonic reactivity, appetite, preference, and even reinforcement learning. Given the slippery and imprecise nature of this term, it is wholly inadequate to attribute specific effects in experiments simply to reward without any qualification or explication.” [Emphasis added]

Salamone, J. D., Correa, M., Ferrigno, S., Yang, J. H., Rotolo, R. A., & Presby, R. E. (2018). The psychopharmacology of effort-related decision making: Dopamine, adenosine, and insights into the neurochemistry of motivation. Pharmacological Reviews70(4), 747-762.

On sleep and creativity

800px-francisco_josc3a9_de_goya_y_lucientes_-_the_sleep_of_reason_produces_monsters_28no-_43292c_from_los_caprichos_-_google_art_projectJust came across a nice little article by Ed Yong on how the two major phases of sleep — REM and slow-wave sleep — might contribute to creativity. These ideas have been floating around for a while, but it’s nice to see them in a pop sci article.

A New Theory Linking Sleep and Creativity

Continue reading

Why human memory is not a bit like a computer’s

DisintegrationofPersistence(This is a cross-post of a 3 Quarks Daily article I wrote last year.)

A few months ago I attended a rather peculiar seminar at MIT’s Department of Brain and Cognitive Sciences. A neuroscientist colleague of mine named Robert Ajemian had invited an unusual speaker: a man named Jim Karol, who was billed as having the world’s best memory. According to his website, his abilities include “knowing over 80,000 zip codes, thousands of digits of Pi, the Scrabble dictionary, sports almanacs, MEDICAL journals, and thousands of other facts.” He has memorized the day of the week for every date stretching back to 1AD. And his abilities are not simply matter of superhuman willingness to spend hours memorizing lists. He can add new items to his memory rapidly, on the fly. After a quick look at a deck of cards, he can recall perfectly the order in which they were shuffled. I witnessed him do this last ‘trick’, as well as a few others, so I can testify that his abilities are truly extraordinary [1].

Continue reading