{"id":31511,"date":"2023-07-28T17:00:37","date_gmt":"2023-07-28T15:00:37","guid":{"rendered":"https:\/\/www.sciencefocus.com\/?p=149621"},"modified":"2023-07-28T17:39:45","modified_gmt":"2023-07-28T15:39:45","slug":"how-tickling-rats-is-revealing-hidden-mysteries-of-the-brain","status":"publish","type":"rss_feed","link":"https:\/\/c01.purpledshub.com\/bbcsciencefocus\/rss_feed\/how-tickling-rats-is-revealing-hidden-mysteries-of-the-brain\/","title":{"rendered":"How tickling rats is revealing hidden mysteries of the brain"},"content":{"rendered":"

More than sensory information and motor commands; there\u2019s an area of the brain also related to play. <\/p>

By Holly Spanner\n \t\t<\/p>

Published: Friday, 28 July 2023 at 15:00 PM<\/p>

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Yes, rats can laugh. But not in the same way that humans do; as an outburst of ultrasonic squeaks.<\/p>\n

And now, scientists are using rat laughter<\/a> to map a part of the brain called the periaqueductal gray (PAG). Found in the midbrain, the PAG is a cell-dense region (also known rather aptly as the \u2018midbrain central gray\u2019), which is key for behavioural responses to threats, and in animals, this includes hunting behaviours in predators and defensive behaviours in prey<\/a>.<\/p>\n

We\u2019ve known for a while now that rats like to be tickled<\/a>; they produce a high frequency (around 50 kHz) laugh in response to what scientists call \u2018manual tickling sessions\u2019. As human hearing tops out at around 20 kHz, special microphones were needed to hear them laughing.<\/p>\n

Through measuring rats\u2019 brain activity (via electrodes implanted into the brain), along with these giggles, researchers from Humboldt-Universitat zu Berlin have determined that the PAG is also essential for play and laughter, publishing their findings in the journal Neuron. <\/em><\/p>\n

\u201cWe know that vocalisations such as laughter are very important in play, which supported the idea that there is some sort of organisation signal in the brain regulating this behaviour,\u201d says senior author Professor Michael Brecht<\/a>, a neuroscientist at the Humboldt-Universit\u00e4t zu Berlin. \u201cFor example, children check for laughter when they play-fight with each other. If their playmate isn\u2019t laughing any more, they stop fighting.\u201d<\/p>\n

Despite it being the universal language of childhood, and one which incorporates learning, experience, knowledge and imagination, play remains one of the least understood forms of behaviour. The neural pathways that control playfulness in either humans, or other animals have remained somewhat of a mystery.<\/p>\n

\"Graphical<\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/picture><\/div>
Increased neural activity was observed in the PAG during tickle-time and playtime (top), but blocking the PAG impaired playful behaviours (bottom). Image credit: Neuron Gloveli et al<\/span><\/figcaption><\/div>\n

\u201cA lot of people think that play is childish or not a very decisive behaviour, but play is underrated,\u201d says Brecht. \u201cIn my perception of play, it\u2019s a self-training behaviour. Usually, brains serve for controlling behaviours. Play behaviour, however, seem to serve for growing brains.\u201d<\/p>\n

After making sure the rats were comfortable in their environment, researchers carried out dorsal tickling (tickling their backs), ventral tickling (tickling their bellies) and played games of \u2018chase the hand\u2019.<\/p>\n

Strong neural responses in the lateral column of the PAG were observed in both tickle-time and playtime, which coincided with these ultrasonic chuckles; they were happy.<\/p>\n

However, when the rats were in an unfamiliar environment designed to provoke anxiety, not only did they stop laughing, but those same cells in the PAG decreased their activity. Likewise, inactivation of the PAG lead to impaired playful behaviours and ticklishness.<\/p>\n

It\u2019s a strong indication that playfulness is instinctual, which ties in with previous research<\/a> that has shown that playfulness persists, even if the cortex, the outer surface of the brain which controls consciousness, fails to develop.<\/p>\n

Next, the researchers plan to compare the playfulness of other species, to see whether similar activity is also observed in the lateral column of the PAG. Another question they are keen on answering, is whether giving younger rats different play habits will change the way that this area of the brain develops as it matures.<\/p>\n

Read more about rats: <\/strong><\/p>\n