Mind Matters Scientific American Community

Mind Matters

Mind Matters

by Mind Matters

56 Entries | 331 Comments

Mind Matters's Blog Categories

Archaeology & Paleontology

Society & Policy

Blog Roll

Monkeys Hear Voices From Mind Matters Apr 8, 2008 Mind & Brain
Introduction By Jonah Lehrer, Editor, Mind Matters The ability to communicate with language is one of the defining talents of the human mind. The evolution of language, of course, depends in large part on the evolution of speech, which allows us to express ourselves and understand the expressions of others. New research… CONTINUE READING>
Close [x] Bookmark this Title Title Description <center><b>Introduction<br><br>By Jonah Lehrer, Editor, Mind Matters</b></center><br><br>The ability to communicate with language is one of the defining talents of the human mind. The evolution of language, of course, depends in large part on the evolution of speech, which allows us to express ourselves and understand the expressions of others. New research suggests that a brain area underlying a specific aspect of speech - namely, an area devoted to processing voices - is not as uniquely human as previously assumed. <br><br><center>_____________________</center><br><center><h3>A Voice Area in the Monkey Brain</h3><br><strong><a href="http://www.psy.gla.ac.uk/staff/index.php?id=PB002">Pascal Belin</a></strong><br /><br>University of Glasgow</center><br><br>The use of vocalizations, such as grunts, songs or barks, is extremely common throughout the animal kingdom. Nevertheless, humans are the only species in which these vocalizations have attained the sophistication and communicative effectiveness of speech. How did our ancestors become the only speaking animals, some tens of thousand years ago? Did this change happen abruptly, involving the sudden appearance of a new cerebral region or pattern of cerebral connections? Or did it happen through a more gradual evolutionary process, in which brain structures already present to some extent in other animals were put to a different and more complex use in the human brain? <br><br>A recent <a href="http://www.kyb.mpg.de/publications/attachments/Petkov%20-%20Voice%20Area%20-%20NatureNeuro%20-%202008_4896[0].pdf">study</a> yields critical new information, uncovering what could constitute the "missing link" between the brain of vocalizing, non-human species and the human brain: evidence that a cerebral region specialized for processing voice, known to exist <a href="http://www.nature.com/nature/journal/v403/n6767/abs/403309a0.html">in the human brain</a>, has a counterpart in the brain of macaques.<br>Neuroscientist <a href="http://www.kyb.mpg.de/~chrisp">Chris Petkov </a>of the Max Planck Institute and his colleagues used functional magnetic resonance imaging (fMRI) to explore the macaque brain. They measured cerebral activity of awake macaque monkeys who were listening to different categories of natural sounds, including macaque vocalizations. They found evidence for a "voice area" in the auditory cortex of these macaques: a discrete region of the anterior temporal lobe in which brain activity was greater for macaque vocalizations than for other sound categories such as natural sounds. This region was observed in several different individuals, even under condition of total anaesthesia. Even more remarkably, the region showed repetition-induced reduction of activity--or neuronal adaptation--in response to different calls coming from a same individual. This finding suggests that this brain region is processing information about the identity of the speaker, a phenomenon that is also observed in the <a href="http://www.zlab.mcgill.ca/docs/Belin_and_Zatorre_2003.pdf">human voice area</a>. <br><br><strong>Long History of Voice?</strong><br>Perhaps the most remarkable implication of this finding is that the voice area previously identified in the human brain is not uniquely human, and that it has a counterpart in the brain of non-human primates. This discovery, in turn, suggests that the voice area has a long evolutionary history and was probably already present in the common ancestor of macaques and humans some 20 million years ago. It's known that the cognitive talents underlying voice perception, such as speaker recognition, are shared with many other animal species, but the findings of Petkov et. al provide a cerebral location for these abilities. <br><br>Ironically, most of the research into the evolutionary basis of language has focused so far on a single function - speech perception - which is unique to humans and thus evolutionary precursors are hard, if not impossible, to identify. The present findings suggest another, possibly more rewarding, strategy: it is perhaps rather by looking at what we have in common with other animals - that is, a rich cerebral substrate to process vocalizations and extract speaker-related information - that will allow us to understand the evolution of speech. Indeed, Petkov et al.'s finding suggests that when our ancestors began to talk, a few tens of thousands years ago, they were already equipped with sophisticated neural machinery specialized in processing voice. <br><br>Another important implication of Petkov et al.'s findings concerns the functional <a href="http://en.wikipedia.org/wiki/Lateralization_of_brain_function">lateralization</a> of the macaque voice area. A well-established property of the human cerebral substrate for speech (particularly speech production) is its lateralization to the left hemisphere. This well-established left-hemispheric asymmetry has led researchers to investigate whether a similar left hemispheric bias could be found in other animals, as a possible evolutionary precursor of human language. Unfortunately, this longstanding belief has possibly resulted in a strong bias in the literature, whereby studies uncovering any leftward asymmetry in non-human primates are much more likely to be published in high-impact journals.<br><br><strong>A Role for the Right</strong><br>A counterintuitive but essential feature of Petkov et al's results, similar to the corresponding findings in the human brain, is that voice-selective activity was stronger in the right hemisphere. Furthermore, the identity-specific neuronal adaptation was only observed in the right hemisphere of the macaque brains, exactly as in the corresponding <a href="http://www.zlab.mcgill.ca/docs/Belin_and_Zatorre_2003.pdf">human studies</a>. This finding suggests that the right hemisphere may well have played a major role in how speech appeared in our ancestors, and that a response to the puzzle of speech evolution may not only lie in the left hemisphere.<br><br>Much work lies ahead before a complete understanding of the functional role of the voice areas, in macaque as well as in humans, can be attained. Several alternative hypotheses remain to be tested: Does the voice area represent hard-wired preference for the particular acoustical structure of vocalizations from that species? Or is it more simply a "formant" detector, a structure specialized in detecting vocal features in general? One other possibility is that this voice area is really a "social" structure, interested in vocalizations because they are important cues for social interaction, and not because they share a particular acoustical structure.<br><br>In conclusion, the findings by Petkov et al. provide an exciting common substrate for high-level, or complex, auditory cognition that can be studied in parallel in humans and macaques. Critical additional information will certainly be obtained in the near future by exploring the monkey voice area using more conventional electrophysiological techniques, such as recording directly from neurons, now that the location of the voice area in the macaque brain has been established. Even more important, this seminal work opens the road for comparative neuroimaging studies in which humans and other animals perform similar tasks and stimuli using similar methodologies, and the results can be analyzed using similar strategies.<br><br>--<br>Edited by Mind Matters at 04/08/2008 1:20 AM<br><br>--<br>Edited by Mind Matters at 04/08/2008 1:20 AM<br><br>--<br>Edited by Mind Matters at 04/08/2008 1:21 AM<br><br>--<br>Edited by Mind Matters at 04/08/2008 1:32 AM Tags Mind_&_Brain Add other tags people have used for this link Posted by Mind Matters Permalink 5 Comments Report Abuse VOTE:
Climbing Mountains Kills Brain Cells From Mind Matters Apr 7, 2008 Mind & Brain
Back in September, R. Douglas Fields, a senior investigator at the NIH, wrote a really interesting post for Mind Matters on the neural hazards of tall mountains.… CONTINUE READING>
Close [x] Bookmark this Title Title Description Back in September, <a href="http://neuroscience.nih.gov/Lab.asp?Org_ID=274" target="_blank">R. Douglas Fields</a>, a senior investigator at the NIH, wrote a really interesting <a href="http://science-community.sciam.com/blog-entry/Mind-Matters/Air-Altitudes-Toll-Brain/300004508" target="_blank">post</a> for Mind Matters on the neural hazards of tall mountains. The post was later turned into an <a href="http://www.sciam.com/article.cfm?id=brain-cells-into-thin-air" target="_blank">article</a> for Scientific American Mind. The causation is rather straightforward, as high altitudes not only starve brain cells of oxygen but can trigger dangerous swelling in the brain, as capillaries begin to leak. In fact, even when mountain climbers didn't experience any symptoms of altitude sickness, MRI scans revealed significant damage. For instance, twelve of thirteen climbers who tried to ascend Mount Everest showed "cortical atrophy or enlargement of the Virchow-Robin (VR) spaces" upon their return.<br><br>The story is now getting some notice. <a href="http://www.aspendailynews.com/section/home/do-14ers-cause-brain" target="_blank">The Aspen Daily News</a>, a locale with some very high peaks, recently interviewed Fields about his article. As Fields notes, “You can react to high altitude quite well, but it takes time. The body’s pretty well adapted to whatever it was evolved to encounter, and it wasn’t evolved to go from sea level to 14,000 feet in one day.” Tags Mind_&_Brain Add other tags people have used for this link Posted by Mind Matters Permalink 1 Comment Report Abuse VOTE:
Recognizing the Familiar From Mind Matters Apr 1, 2008 Mind & Brain
_____________________ Is Familiarity Different Than Remembering? Brock Kirwan UCSD Have you ever had the experience of seeing someone in the grocery store that you know you've already met, but you can't quite remember where… CONTINUE READING>
Close [x] Bookmark this Title Title Description <center>_____________________</center><br><center><h3>Is Familiarity Different Than Remembering?</h3><br><strong><a href="http://whoville.ucsd.edu/kirwan/index.html">Brock Kirwan</a></strong><br /><br>UCSD</center><br><br>Have you ever had the experience of seeing someone in the grocery store that you know you've already met, but you can't quite remember where or when you met them? In other words, you have a feeling of familiarity, even if you can't remember what, exactly, this familiarity is based upon? Compare this experience with what happens when you meet someone whom you recognize immediately, and can remember lots of relevant details about. (For instance, you can remember his or her name, or the last time you met.) <br><br>These examples illustrate the two processes that psychologists and cognitive neuroscientists believe are at work when we remember someone or something: a general feeling of familiarity and conscious recollection of specific details. The idea that recollection and familiarity are (at least psychologically) distinct is uncontroversial. There are many conditions that affect one process but not the other. A more controversial subject is whether the two processes are neurally distinct. That is, do they depend on different brain structures? <br><br>Sauvage and colleagues attempt to address this question in a recent paper in the journal <a href="http://www.nature.com/neuro/journal/v11/n1/abs/nn2016.html">Nature Neuroscience</a>. They took a group of rats and trained them on a recognition memory task in which they presented a series of odors mixed into a digging medium. For instance, the rats were given cumin scented wood chips or sand that smelled of thyme. Then they gave the rats a "test list" following a delay. Half of the items on the "test list" were the same odors and mediums that the rats had been exposed to earlier, whereas the other half were new combinations. Rats that got cumin wood chips now might be supplied with cumin-scented sand or glass beads coated in that spice. The rats were trained to make one response to the old pairs and another response to the rearranged pairs. The critical comparison was between the performance of a group of rats that had received a lesion to the hippocampus (a brain structure known to support declarative memory, or memory for facts and events) and a group of control rats with no lesion.<br><br>The innovative part of the study is that Sauvage and colleagues were able to vary the incentive the rats had for making correct decision by controlling the amount of the reward and the difficulty in obtaining the reward. This allowed the researchers to plot the hit rate (correct responses to a target) against the false alarm rate (incorrect responses to a new, or in this case re-paired item) at several different levels. This kind of plot is called an <a href="http://en.wikipedia.org/wiki/Receiver_operating_characteristic">ROC curve</a> and has been used in psychology to describe people's performance on recognition memory tests. If the participant is randomly guessing, then the ROC will be a straight line from the bottom left of the plot to the top right. The better the performance, the higher the curve will fall above that diagonal. As with any curve, it can be modeled mathematically and, as with most curves, it can be modeled in more than one way.<br><br>Sauvage and colleagues consider two models. The first model assumes that the ROC can be described by a single memory-strength continuum, in which familiarity is simply a weaker form of memory than recognition, but still the same form. The second model assumes that the ROC is described by separate recollection and familiarity processes in the brain. This latter example is known as the dual process model. <br><br>Here's the tricky part: When the authors probe how well each model describes the data from the control rats and rats with hippocampal lesions, both models do a pretty good job. The difference between the predictions of the two models and the data is not significantly different from zero, although the dual process model is slightly better. In other words, there is no statistical reason to prefer one model over the other based on how well the models fit the behavioral data. The authors do offer some additional evidence for why they favor the dual process model, but this information relies on a subtle statistical argument that isn't typically used in ROC analyses. <br><br>For instance, if we assume that the single strength memory model is correct, it appears that the lesioned animals simply have weaker memories relative to the controls. (This finding shouldn't be too surprising because we know that the <a href="http://en.wikipedia.org/wiki/Hippocampus">hippocampus</a> is involved in memory for facts and events). If we assume the dual process model is correct, however, then it appears that the data from the hippocampal lesion animals fall along a curve (indicating that the rodents relied entirely on familiarity to solve the task) whereas the data from the control animals falls along a straight line (indicating that they used recollection only). But both possible explanations make sense.<br><br>This last point, that the control animals have a straight ROC, is remarkable considering that one almost never sees that in the human recognition memory literature. Indeed, it is usually assumed that people rely on both recollection and familiarity in recognition memory tasks. It would seem, then, that either this task taps something other than what people use in solving recognition memory tasks, or that rats solve the task in a fundamentally different way than humans do. Both possibilities merit further investigation.<br><br>--<br>Edited by Mind Matters at 04/06/2008 1:04 PM Tags Mind_&_Brain Add other tags people have used for this link Posted by Mind Matters Permalink 1 Comment Report Abuse VOTE:
The Power of Power Naps From Mind Matters Mar 25, 2008 Mind & Brain
_____________________ Tired? Take A Nap Jessica Payne and Matthew Walker Harvard University and University of California at Berkeley Sleep is… CONTINUE READING>
Close [x] Bookmark this Title Title Description <center>_____________________</center><br><center><h3>Tired? Take A Nap</h3><br><strong><a href="http://www.isites.harvard.edu/icb/icb.do?keyword=k3007&pageid=icb.page14991">Jessica Payne</a> and <a href="http://psychology.berkeley.edu/">Matthew Walker</a></a></strong><br /><br>Harvard University and University of California at Berkeley</center><br><br>Sleep is such a fundamental biological drive that it's shared by practically every species, from fruit flies to humans. Indeed, sleep is so essential that animals will die as quickly from sleep deprivation as they will from food deprivation. And yet despite such alarming evidence (not to mention all the things your mother told you about the importance of sleep), human beings are one of the few species that deliberately deprive themselves of sleep. Why do we do this? Most would blame the frantic pace of modern life: we live in a 24/7 world, fuelled by ever-present deadlines, demands and responsibilities. With so much to do and so little time, it seems tempting, or perhaps even necessary, to shave off a few hours of sleep in order to get things done. Given this chronic shortage of shuteye, wouldn't it be wonderful if a quick nap could refresh us mentally and improve our memories? Results from a recent study by <a href="http://www.blackwell-synergy.com/doi/abs/10.1111/j.1365-2869.2008.00622.x">Lahl et al.</a> (2008) suggest that a mere six-minute nap may be able do just that. <br><br>Before discussing this intriguing finding, some background is in order. The past decade has witnessed a boom in reports demonstrating that sleep after learning is critical for the offline "consolidation" of memories. The process is what allows the brain to convert newly learned information into long-term storage in the brain. Sleep has been shown to promote consolidation of various kinds of memory, from <a href="http://nro.sagepub.com/cgi/content/abstract/12/5/410">procedural skills</a> (for example, learning to play a musical instrument or mastering a sport), to <a href="http://www.americanscientist.org/template/AssetDetail/assetid/51962">episodic memories</a> (such as remembering facts and experiences learned during the day). These benefits were initially thought to require a full night of sleep, but more recent studies suggest that, for episodic memories, a 60-to 90-minute nap may generate the same <a href="http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WNM-4JVSVPM-3&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=5263c5bd8229aec9b9959877b5d580f6">memory benefits</a> in much less time. Until the study by Lahl et al., however, many scientists would have been skeptical about the efficacy of a nap that was any shorter. In part, this skepticism is because the biological mechanisms believed to be necessary for cementing long-term memories - particularly the synthesis of new proteins needed to strengthen synaptic connections - takes at least this long. Nonetheless, there are many anecdotal accounts describing the cognitive benefits of ultra-short "power naps." The study by Lahl et al. provides the first empirical support for such a claim.<br><br>In this study, 18 college students participated in three different experimental conditions: taking a long nap (35 minutes), a short nap (six minutes) or remaining awake. Prior to napping (or remaining awake), participants learned a list of 30 words and were tested on these words one hour later. Learning always took place at 1 P.M. and testing took place at 2 P.M.; the question was whether napping would produce better memory retention than wakefulness. The short nap consisted of relatively light sleep, mostly stages 1 and 2 non-rapid eye movement (NREM) sleep. The long nap contained even more of this light sleep, along with about 10 minutes of deeper slow-wave sleep (stages 3 and 4 NREM). Similar to a previous <a href="http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WNM-4JVSVPM-3&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=5263c5bd8229aec9b9959877b5d580f6">study</a> by Tucker et al. (2006), the long nap resulted in better memory for the words than wakefulness. But, remarkably, so did the short nap, albeit at a lower level. Nevertheless, this suggests that just six minutes of sleep can produce significant memory benefits. <br><br>As interesting as these findings are, several questions remain. First, participants were tested after just one hour, leaving unclear whether the memory improvement persists long term (a defining characteristic of consolidation) or is simply transitory. Would a mere six minutes of afternoon sleep promote improved recall one day or even one week later? Second, it is important to keep in mind that the memory improvement seen by Lahl et al. is modest. The long nap increased recall above wakefulness by about two words, and the short nap by a little more than one word. This finding leaves open questions about the utility of such short sleep, relative to obtaining a full night. Perhaps most intriguing of all is the underlying mechanism that generates these effects. Is there something about the neurobiology of sleep that enhances memory, even in short bursts? Or is it the lack of deleterious waking mental activity, which might interfere with memory storage? Because no specific stage of sleep correlated with the memory benefit, we are left hunting for clues. It is hard to imagine any known biological processes operating quickly enough to create the new synaptic structures necessary for memory consolidation within such a short timeframe. However, one possible answer resides in the electrical signals of sleep. For example, short nappers obtained a few minutes of stage 2 sleep, a stage that produces "sleep spindles." These powerful synchronous bursts of electrical activity have been linked to <a href="http://www.ncbi.nlm.nih.gov/pubmed/11119697?ordinalpos=2&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSum">memory stabilization</a>. Alternatively, such short naps may not necessarily change the strength of the memory, but rather allow easier access to it. That is, sleep, and just a small amount, may "grease" the recall-shoot that memories slide down, allowing easier access to the material. Yet another idea is that ultra-short naps may rapidly refresh regions of the prefrontal lobe (which suffer the greatest burden when sleep deprived), and, as a result, allow the brain to more accurately search its storehouse of memories.<br><br>Regardless of one's interpretation of the results, the experimental benefit of napping seems clear. This finding should come as good news for those of us who feel guilty or lazy for napping⎯an unfortunate reflection of a society out of touch with our basic biological needs. Nonetheless, we should still remember what our mothers might say: "a nap is no substitute for a good night's sleep." Maybe it is time we all woke up to this reality. Tags Mind_&_Brain Add other tags people have used for this link Posted by Mind Matters Permalink 6 Comments Report Abuse VOTE:
The Reading Brain From Mind Matters Mar 18, 2008 Mind & Brain
_____________________ Routes to Reading Maryanne Wolf, Mirit Barzillai, and Elizabeth Norton Tufts University Reading changed the… CONTINUE READING>
Close [x] Bookmark this Title Title Description <center><img alt="0.jpeg" src="http://scienceblogs.com/cortex/0.jpeg" width="78" height="120"/></center><br><center>_____________________</center><br><center><h3>Routes to Reading</h3><br><strong><a href="http://ase.tufts.edu/crlr/">Maryanne Wolf, Mirit Barzillai, and Elizabeth Norton</a></strong><br /><br>Tufts University</center><br><br>Reading changed the course of intellectual development in our species. Over the span of approximately 5,000 years, we moved from societies in which literacy was extremely rare to a highly technological world in which the ability to read is practically a prerequisite for survival. Although many research paradigms attempt to reveal how the human brain learns to read, few are more interesting and instructive, perhaps, than the methods and questions of cognitive neuroscience. <br><br>The story of reading's development is a <a href="http://www.amazon.com/Proust-Squid-Story-Science-Reading/dp/0060186399/ref=pd_sim_b_title_2">complex tale</a> of equal parts human invention and neural plasticity. The human mind created reading, but that skill could only come about because of the brain's unique capacity to form new circuits. Scientists have long known that reading depends on an intricate set of neural circuits in the brain, but the exact operation of these circuits remains an area of ongoing investigation. Now, a <a href="http://www.ncbi.nlm.nih.gov/pubmed/18182174?ordinalpos=3&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSum">study</a> by cognitive neuroscientists Laurent Cohen, Stanislas Deaene and their colleagues in the March 1st issue of the journal Neuroimage gives us some new insights into the reading brain.<br><br>Cognitive neuroscienists often break down the study of reading into its components, including processes that are phonological (related to the sounds of language), orthographic (related to the way a language is written t), and semantic (related to meaning). In their <a href="http://www.ncbi.nlm.nih.gov/pubmed/15951224">seminal work</a>, Cohen, Dehaene and their colleagues concentrated on orthographic processes. In doing so, they have pushed our understanding of what the brain does when it reads anything from the smallest features of letters; oft-repeated letter patterns (such as the "ph" or "ent" in English); to words that vary in length, frequency of usage, position (where the eyes fixate when reading them) and the overall quality, or legibility of presentation. Using imaging methods, Dehaene, Cohen and their colleagues have added