Although I know this is probably not the place, I feel duty-bound to say that my riot-running days are over. When past form includes enough time spent in the local hospital to be on first-name terms with the casualty dept. doctor and your only social contact consists of friendly phonecalls from a teenage Turkish smack dealer, it might be time to direct your energies elsewhere. But, while anecdotes of Berlin misadventure are thin on the ground, it does mean I have been able to visit the latest exhibitions on Brunnenstrasse, Berlin's best street of galleries. In this way it far surpasses its older neighbour Auguststrasse, still mostly flogging a decorative dead horse and, regardless, in the opposite direction of my office-second home-nearest off-license, the Internet cafe.

After two months in the remembrance service for itself otherwise known as New York, I have come back to find that change is in the air. The Johnnz Cash imbiss (=chuck truck), so called because it not only served cheeseburgers night and day but soundtracked it to non-stop Man in Black, is boarded up. Across the street, meanwhile, the quasi-Portuguese cafe that resembles an ersatz torture chamber where the prisoners have been exchanged for media workers, their haircuts, and their offspring, is thriving. The local bars that only close when the owner falls over are an endangered species, while the 5-Euro sandwich spreads amoebically. Topographers of loss do not want for subject matter in Mitte.

It is a subject taken up on Brunnenstr., too, both with the new spaces opening (Pitrowski Galerie at no. 5, the relocated Foto-Shop at no. 11, Galerie Gillian Morris at no. 3) and the exhibitions stages. At Curators Without Borders, a group show entitled Berlin's Urbanity in Contemporary Art explores a "common visual and linguistic discourse about the so-called 'New Berlin'". The wordy title and wordier text are giveaways, though, for a show that jumps through curatorial and verbal hoops to dress up an ordinary treatment of very familiar themes. Some of the work, Elin Jakobsdottir's Horsebox especially, is worthy, but the show still looks and feels like an idea, and a wordy one, in search of its artists.

Elsewhere, at Gillian Morris and Pitrowski, the attention paid to video and isntallation gives further indication of the changes afoot. The painterly, figurative tendency of the Berlin art world seems to be giving way to a more challenging vocabulary. Work is becoming more gripping, possibilities riper. Heady times, even if it is no compensation for a Johnny Cash burger on the ugly splendour of Rosenthaler Platz.

This doesn't mean, however, that art in more conventional media isn't also in evidence. Norbert Witzgall's paintings, at Nice & Fit (Brunnenstr. 13), recall in style and subject (kitschy women, a queasy-coloured dog) a trashy, DIY aesthetic familiar from so many Berlin shows. Filiale (Brunnenstr. 188-190) meanwhile hosts a group show of abstract paintings which I'll pass over to the abstract-minded, with the note however that their next show, of Anja Shrey's monumental pen and paper figures, promises to be excellent.

Best by far, though, is to be found in the rear courtyard of Brunnenstr. 10, at Galerie Ben Kaufmann. Poul Gernes (1925-1996) is known mostly for his large, colourful works: his abstract designs decorate public and commercial spaces throughout his native Denmark. The photographs in 'Behind', though, are different. They are also brilliantly literal, a series of black and white rear ends as carefully detailed as portraits. Balls and pussies push, ooze, or attempt to retreat between closed thighs. Little else can be made out, yet if these photographs are as detailed as portraits they are also as distinct. No two are alike, and the more you look the more the expanses of thigh, the shadowy passages of genitalia take on a life of their own.

There is humour here, but also a kind of solemnity. The photographs, with their careful details but greyscale contrasts, resemble not so much photocopies as x-rays. Around the space they form a ghostly parade, intimate and still ludicrous - balls from below look very silly indeed, like overcooked sprouts. A pathos forms around them and is amplified by the plaster cast in the centre of the gallery of an anonymous arse where, if you peer in, you can tace the indentations of tiny hairs. Between them, as much as there is joyful glee in each delineated posterior, there is the sadness of an absent presence: death masks, Turin Shrouds.

What I'm trying to say is that as much as 'Behind' reminds me of one of my father's jokes - "What do you think of the rectum as a whole?" "I think it's a dirty crack and should be wiped out." - it also recalls Celine: "I couldn't make up my mind to show them my truth; it was as unworthy of them as my rear end."

Change of course has another face or, if you like, a rear end as well. Goff and Rosenthal's (Brunnenstr. 3) exhibition of Scott Hunt's drawings of kitsch, perverse Americana are competent if unspectacular. I am visiting with my friend Stefano Castronovo, a recent emigre from New York and distinguished painter in his own right, on a tour of galleries. We enter and he asks for further information about the show. Icily the square-jawed manageress emerges from her hidey-hole and points us towards the postcards with a clipped Home Counties malevolence I thought I'd left behind. Stefano and I futz around with them while her eyes hover somewhere at our backs. Undeterred, wanting to orient himself in a new town, Stefano asks to speak with Mr/Mrs/Master/Miss Goff and/or Rosenthal. "They're not here," the manager snaps and boats back behind her partition. We step onto the street, where the smell of kebab meat feels refreshing.

You know your city's made it when it imports gallery attendants who make you feel like you're about to be told off by a teacher. Or, to put it another way, for every sublime posterior there's a purblind arse.

Maybe it's time to run riot again.