TROPICAL SYNAPSES
Reflections on topics including clinical neurology, recent publications in neuroscience,
philosophy of biology, "neuro-doubt" about modern media hype of new neuro-scientific procedures and methods, consciousness, scuba diving, horticulture, jazz, blues, slack key guitar music, the Hawai'i health scene, and whatever else dat's da kine...
It may not be unimportant for the investigator of nature to consider and recognize the indetermination which the law of causality leaves over. To be sure, the only value of this for him is to keep him from transgressing its limits. On the other hand, an idle philosopher could perhaps connect his ideas on freedom of the will with this, with better luck than he has had hitherto in the case of other gaps in knowledge.
Human and other animal behavior and physiology commonly show a circadian rhythm, a change in behavior that follows an approximate 24 hour cycle. Animals and humans also show patterns in their behavior, such as mealtime intervals, that are not fixed to the approximately 24-hour circadian cycle, but instead have periods that are substantially less than (i.e., ‘ultradian’) or greater than (i.e., ‘infradian’) 24 hours (see also this review).
The article below suggests that both ultradian and infradian rhythms may be set by the dopaminergic system. Deliberately altering such settings might some day help the insomnia disorders so common in those with mental illnesses as well as sleep disorders in conditions such as Parkinson disease.
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ABSTRACT
A highly tunable dopaminergic oscillator generates ultradian rhythms of behavioral arousal
Ian D Blum, Lei Zhu, Luc Moquin, Maia V Kokoeva, Alain Gratton, Bruno Giros, Kai-Florian Storch
DOI: http://dx.doi.org/10.7554/eLife.05105
Published December 29, 2014
Ultradian (∼4 hr) rhythms in locomotor activity that do not depend on the master circadian pacemaker in the suprachiasmatic nucleus have been observed across mammalian species, however, the underlying mechanisms driving these rhythms are unknown. We show that disruption of the dopamine transporter gene lengthens the period of ultradian locomotor rhythms in mice. Period lengthening also results from chemogenetic activation of midbrain dopamine neurons and psychostimulant treatment, while the antipsychotic haloperidol has the opposite effect. We further reveal that striatal dopamine levels fluctuate in synchrony with ultradian activity cycles and that dopaminergic tone strongly predicts ultradian period. Our data indicate that an arousal regulating, dopaminergic ultradian oscillator (DUO) operates in the mammalian brain, which normally cycles in harmony with the circadian clock, but can desynchronize when dopamine tone is elevated, thereby producing aberrant patterns of arousal which are strikingly similar to perturbed sleep-wake cycles comorbid with psychopathology.
DOI: http://dx.doi.org/10.7554/eLife.05105.001
Damage to Broca's area in the anterior perisylvian cortex of the frontal lobe produces hesitant, broken, incomplete speech, termed Broca's aphasia. Because of the tendency to attribute specific functions to the same areas that, when damaged, result in loss of that function, Broca's area has been felt to be directly responsible for speech production in humans. As usual in the brain, the story is more complicated, as Finker et al in the study below show.
Patients who, generally due to epilepsy, had implanted cortical electrode arrays directly on Broca's area and nearby motor cortex were studied during conversation. It was demonstrated that Broca's area is active just before speaking, but is relatively inactive while speech is being uttered. This suggests that when we are deciding what to say, Broca's area encodes a motor sequence, presumably of phonemes, that is subsequently executed by motor cortex as our actual speech. It's as if the message is first written by Broca's area and then, about a half second later, that message is "printed out" by motor cortex controlling our bodies to speak the sounds of the words. On the article's second page, in a sentence that revises textbook understanding of speech production in humans, the authors state:
This temporal window of activity constrains Broca's area processing to pre-articulatory stages rather than to the on-line coordination of the speech articulators.In other words, speech production is highly modularized between semantics and phonemic "articulatory codes." Lingustics has tried to divide semantics and syntax, but the brain seems to divide language at the level of the phoneme, with semantics perhaps then including everything above that dividing line.
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PNAS Early Edition > Adeen Flinker, doi: 10.1073/pnas.1414491112
Redefining the role of Broca’s area in speech
Adeen Flinker, Anna Korzeniewska, Avgusta Y. Shestyuk, Piotr J. Franaszczuk, Nina F. Dronkers, Robert T. Knight,, and Nathan E. Crone
Edited by Mortimer Mishkin, National Institute for Mental Health, Bethesda, MD, and approved January 26, 2015 (received for review August 4, 2014)
Significance
Broca’s area is widely recognized to be important for speech production, but its specific role in the dynamics of cortical language networks is largely unknown. Using direct cortical recordings of these dynamics during vocal repetition of written and spoken words, we found that Broca’s area mediates a cascade of activation from sensory representations of words in temporal cortex to their corresponding articulatory gestures in motor cortex, but it is surprisingly quiescent during articulation. Contrary to classic notions of this area’s role in speech, our results indicate that Broca’s area does not participate in production of individual words, but coordinates the transformation of information processing across large-scale cortical networks involved in spoken word production, prior to articulation.
Abstract
For over a century neuroscientists have debated the dynamics by which human cortical language networks allow words to be spoken. Although it is widely accepted that Broca’s area in the left inferior frontal gyrus plays an important role in this process, it was not possible, until recently, to detail the timing of its recruitment relative to other language areas, nor how it interacts with these areas during word production. Using direct cortical surface recordings in neurosurgical patients, we studied the evolution of activity in cortical neuronal populations, as well as the Granger causal interactions between them. We found that, during the cued production of words, a temporal cascade of neural activity proceeds from sensory representations of words in temporal cortex to their corresponding articulatory gestures in motor cortex. Broca’s area mediates this cascade through reciprocal interactions with temporal and frontal motor regions. Contrary to classic notions of the role of Broca’s area in speech, while motor cortex is activated during spoken responses, Broca’s area is surprisingly silent. Moreover, when novel strings of articulatory gestures must be produced in response to nonword stimuli, neural activity is enhanced in Broca’s area, but not in motor cortex. These unique data provide evidence that Broca’s area coordinates the transformation of information across large-scale cortical networks involved in spoken word production. In this role, Broca’s area formulates an appropriate articulatory code to be implemented by motor cortex.
This book is a voluminous, painstakingly documented work, with almost half of its 408 pages devoted to references. The book reviews the song of humpback whales as a cultural phenomenon which changes over the years as innovations in the song are copied among singers. It makes a case for the dolphin's use of a unique click signature for each individual in the local pod, and explores the passing of specific foraging skills between older and younger members of pods of killer whales and dolphins, and how this has been shown to be relatively independent of genetic heredity. I found its detailed descriptions of cooperative fishing between humans and dolphins, something still occurring today in South America, and past cooperative whaling between orcas and humans on the Australian coast especially intriguing. The book also reviews evidence for sperm whale clans, organizations over huge regions of oceans which share similar dialects of "coda" whale song, again in patterns which suggest learning after birth, not heredity.
The book is cumulatively quite convincing in this assertion: there is excellent evidence for, and little evidence against, the belief that various species of cetaceans show evidence of communication as a path to the learning of, at minimum, foraging techniques and social skills.
The philosophical question: is this learning and communicating in cetaceans really the same thing which we call culture in ourselves? Whitehead and Rendell devote two entire chapters (chapters 2 and 8) to this question. These two chapters depart from the authors' thoroughly illuminated documentation of cetacean behaviors and venture into the less lit boundaries of theoretical biology, sociology, and philosophy. Thoughtful, objective despite the authors' declared position, and thorough, these chapters might do well as excerpts in college classroom readings in the philosophy of science.
So what is the case for cetacean culture on the philosophical side? The authors point out their difficulty, despite their evidence. The Bayesian biases are clear: in biology, we look first for an explanation of human behavior in their culture and first for an explanation of nonhuman animal behavior in their heredity (Morgan's Canon).
The case seems to be as follows:
Then, by the above definition, the book provides empirical evidence for definite culture in:
The book lists many other instances that are less well shown as cultural behaviors, by their definition. The case is thus one of accumulating empirical evidence that cetaceans show culture as defined above.
What of the definition? Is it compatible with what humans consider culture? Yes, but only in a greatly impoverished sense. Cetacean cultures lack the aspects that are uniquely ours as humans, those unique to sophisticated uses of language and technology. But by convincingly documenting the evidence that cetaceans, too, have culture, the authors may have both widened views of nonhuman sentience and narrowed the scientific understanding of what it is that is uniquely human.
I disagree in part: I think pain is a vertebrate, c-fiber, sensory perception which drives avoidant behavior, all of which fish definitely have. There may be an analog to such function in invertebrates, but there I am less certain about pain.
Suffering, though, requires the higher cognitive faculties which Dr. Key says are required for pain as such. He gives a very good review of the relevant neuroanatomy in his post.
So we have what amounts to a mere difference in definition. I'd say Dr. Key's "pain" is what I term "suffering." I agree that it is unlikely that fish can suffer. So go ahead, bait that fishhook. Or, if you find yourself feeling badly for the fish (for a rather unconvincing counterpoint, see here), you can confine yourself to eating just the nori :).
In a printed posted to the medRxiv preprint archive this month, I found a chart review of patients with stroke to determine factors (other t...
